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Darth Edris: would probably stash it away as she secretly controls all of Equestria's money anyways

Blue Banana: would probably upgrade or buy a new costume

Cosmica Emerald: Materials for some scientific experiments

Heartbreak: Either the same thing as Blue Banana, or a whole bunch of art equipment for making her own comics.

Roach: A whole bunch of journals and diaries to write about his discoveries

Stencha: Some lovely smelling flowers and air fresheners

7874788
That's a tricky question since money isn't really the driving force for many on my characters.

Kaiyo
He controls atoms, why buy when he can create? Buy service, maybe, but he likes to challenge himself.

Second Wind
That... hmm... I'm not very sure. He's in the guard, so I'm guessing he has free room and board, but what would he like personally?

Sol
He doesn't live off much, he might even receive some off the streets to get a drink, but he's basically a wondering spirit with no reason to live, but too afraid to die.

Yimeck
Him? A $1000? That's a ha'penny compared to what his corporation gains in an hour.

Truffles
She might use it to buy detective novels, pay for food, I can't really say. Her society works off the bartering system, but currency is slowly being introduced.

Brook
She's a little fairy, so childish things like candy, sweets, toys.

"What am I even supposed to do with this strange green paper?"