A short lesson in economics, and something else
Luna had absolutely, positively, 0% of an idea of what was going on.
She and Celestia had just been talking, during a relaxing lunch of daisy sandwiches. And all of a sudden, Celly had stood up with a look of firey determination in her eye, hurriedly told Luna to meet her in her study in five minutes and rushed out of the room, muttering something about the relative merits of various introductory Economics textbooks.
Luna had followed her sister's instructions, out of pure curiosity more than anything else, and had just sat down in a comfortably burgundy easy chair when Celestia burst into the room, carrying at least twenty thick books with her magic and breathing heavily.
“This, stops, now,” Celestia said, panting. “This—this ignorance cannot continue on any longer. Schoolfillies know this stuff, and yet a Princess of Equestria does not.”
“...know what?” Luna asked.
Rather than answering her question, Celestia set all of the books—except one—down on her desk. The last she let fall onto Luna's lap. Its title: Economics 101.
“Oh no, not this again!” Luna groaned. “I don't need to learn this stuff. That's what Econom—Econami--Economicists are for.”
“Just the fact that the word economist does not have a place in your vocabulary is appalling,” Celestia said dryly. “Open the book to page iii, Luna, and read aloud.”
Luna read in a droning, robotic voice: “The word economy comes from the Greek word oikonomos, which means 'one who manages a household'. At first, this origin might seem peculiar. But in fact, household and economies have much in common--” Luna interrupted herself, looking down at the book in disgust. “No they certainly do not! Households are places to live, and economies are places to buy and sell things. They're completely different things! This is garbage!” she said, throwing the book to the floor.
Celestia caught the book in her magic and hovered it back into Luna's lap. “Don't throw books,” she said, as if reciting a playground rule, “for they are our closest friends.”
Luna rolled her eyes. Only Celestia would say something so utterly bookwormish.
“And if you would continue to read, you would know that the book is comparing an economy to a household because both have to face tradeoffs. Tradeoffs are the building blocks of any economic system, so understanding their applications is important to any student of economics.”
“Well I don't need economics!” Luna said. “I've gotten along without it just fine so far.”
“Times are changing, Sister,” Celestia said in her I'm-trying-to-be-patient-but-I'm-going-to-snap-soon voice. “We can't just pass laws whenever we feel like it. In order to pass a law, we have to discuss the details and implications of every minor decision with experts. How are you supposed to discuss taxation laws with twenty economists if you don't even understand the basics of supply and demand?”
“But I do,” Luna said stubbornly.
“What about what you said at lunch today, huh?”
“What about it?”
“You said that everypony loved daisy sandwiches, but they couldn't have them very often because daisy sandwiches are so expensive. And then you suggested that stores make daisy sandwiches less expensive so that everypony can afford to have them more often.”
“Yeah, so?”
Celestia looked like she was about to explode. “That's not—how could you—it doesn't make any sense!” she finally outburst. “First of all, the cardinal rule of economics is that you can't just set the price like that! That would mean not having a free market, which is inefficient! And bad! And even besides that, no seller in their right mind in a competitive market like the daisy sandwich industry is just going to lower their prices like that! The sellers are already just barely getting by as it is! And even if the sellers out decide to do that, some would go out of business because of reduced revenues! Meanwhile, more and more ponies would want to buy daisy sandwiches, but there would be less and less on the market...and soon, daisy sandwiches are nothing but a rare commodity ponies have to pay fifty bits on the black market for. You've done the exact opposite of making daisy sandwiches available for all—you've completely wiped them from the market.”
Luna furrowed her brow. “That doesn't make any sense...since more ponies would want to buy the daisy sandwiches, that would mean that the sellers get more revenue! So lowering the price would make things better for all ponies!”
Celestia facehoofed and groaned. “No...it doesn't work like that. At all. Just...no.”
“And how do you know?” Luna asked.
“Economics! Game Theory! Supply and demand! Price ceilings cause shortages!” Celestia said, gesturing wildly to the book. “Luna, you have to learn this stuff. You're making yourself look like—like an idiot by being so ignorant!”
There was silence.
“What did you just call me?”
“Luna, I'm sorry, I--”
“You—you just called me—an idiot.”
“I didn't mean it like that--”
“Of course you didn't, of course you didn't,” Luna said wildly. “Feel free to explain what you meant to say. After all, I'm too much of an idiot to read between the lines--”
“Luna! You know I don't think of you like that!” Celestia cried.
“That's right,” Luna said sourly. “You don't think of me like that. Everypony thinks of me like that. 'Oh, look,' they say, 'there's the Great Goddess and Regal Pony Princess of the Sun! Our very own Princess Celestia! She's smart and pretty and knows everything and ruled Equestria single-hoofedly for a thousand years, overcame so many of the kingdom's problems all on her own—and then there's her little sister. Nightmare Moon—one of Equestia's most dangerous threats since Tirek himself, not really able to do anything except scare ponies away.' This is what ponies say behind my back! I just stand in your shadow, literally the night to your day!”
“Luna, I--”
“Maybe that's what my cutie mark means,” Luna continued. “Why have your destiny be to bring upon the night where your big sister manages it just fine over the span of a thousand years? Do you know how it feels, to not only be completely replaceable, but unwanted? Of course you don't—you're Princess Bucking Celestia. Everypony loves and respects you, but nobody feel the same way for me!”
Luna was crying, and Celestia leaned in closer to nuzzle her sister.
“Don't touch me,” Luna said, voice slightly shaking as tears streamed down her face. She pushed a startled Celestia away. “I just want to be alone,” she said softly, then raced out of the room.
–
Luna was sprawled across her bed, not with the intention of sleeping, even though it was the middle of the night. She heard knocking on her door, with no voice of identification. After all, it was obvious who was there. “Go away. I said, I want to be alone.”
Celestia opened the door and trotted over to Luna's bed. “It's almost dawn,” she said softly.
“Great. Rub it in to me that it is once again time for you to outshine my night. Very tactful of you, sister.”
“I was wondering if you wanted to raise the sun for me.”
Luna turned to face her sister in shock, trying to dry her face plastered with tears as best as she could.
“Since you can handle the moon and all of the stars, it shouldn't be any trouble for you,” Celestia said. “Look—I'm sorry, for letting you go on feeling the way you feel for so long and not only not noticing it, but not doing anything about it. This is my peace offering to you.”
“Raising the sun for one day is much different than raising the moon for a thousand years,” Luna muttered.
“You know just as well as I that the first time is more special and meaningful than all the other times put together,” Celestia said evenly.
It took Luna a few pregnant moments of deliberation before curtly nodding a 'Yes'.
The two sisters teleported to the East Tower. For a while, they watched the stars swim slowly in the sky in silence.
Then, Luna spoke: “It's time.”
She let her magic grasp the moon and stars and slowly let them disappear, letting her magic take care of the finer details automatically. Closing her eyes and concentrating harder, she grasped around space with her magic until she located the sun. For the first time in her life, she felt its firey warmth spread through her body as she pulled it up, and let the light slowly crawl over all of Equestria and beyond like a warm blanket. As the sun was fully pulled over the horizon and all of the stars were tucked under it, Luna let go of the moon, sun and stars with her magic and let out a breath she didn't know she had been holding.
“I did it,” she whispered, not to Celestia, but for the whole world to hear.
Celestia, who had been standing behind Luna and had left a respectful distance of a few yards between the two of them while Luna was at work, now trotted forward to give Luna a quick hug from behind.
“If you call yourself replaceable because I can move the moon and stars, then I am just as replaceable as you,” Celestia said. “The moon and sun do not make us who we are—alone, they are just heavenly bodies, just objects in the sky. It is only together that they can make something whole; by complimenting each other they both grow stronger.” Celestia paused. “Luna, though my sufferings obviously do not even begin to compare to yours, those thousand years I had to live without you were the most miserable years of my life. I love you, Sister, and I need you. Other ponies come and go through the years like waves in an ocean, but with you at my side, I have one thing constant—a sister who always loves me and, no matter what happens, whom I will always love dearly.”
There was a long silence, filled with nothing but the soft whooshing of the wind.
“Celly?” Luna said tentatively.
“Yes?”
“I think—I think I'm want to give that Economics lesson one more try. I'm not promising a sudden mastery of the field, but I'm willing to give it an effort.”
“Oh, Luna, you don't have to do that!”
“I want to,” Luna said firmly. “Now, what was that about an economy being like a household? Something about trade-ins or trade-throughs--”
“Tradeoffs,” Celestia said, giggling slightly. “A situation that involves losing one quality over gaining another. For example, if you take a normal household—wait, before we go to far, maybe we should go back to the study for this. You probably want to be taking notes.”
“Maybe we should,” Luna said, grinning, until she fully realized what Celestia had said. “Wait, note-taking? Does this mean I'll be taking exams as well?”
“Not just exams,” Celestia said, as if it were the most obvious thing in the world, “also midterms, tests, quizzes, pop quizzes, oral reports, ...”
And Luna groaned playfully, though a small part of her was secretly looking forward to it all.
They left the East Tower and the view of the rising sun, walking side by side through the halls of the Canterlot Castle and making their way to the study.
The days, seasons and years would change; ponies would come and go—but in that moment, both sisters knew that no matter what would happen in the future, they would always have each other.
Author's Note
Comments on what you thought of this story are always appreciated. 
