Karen appreciates her gemstones! She has also gotten people things - her generic present is a potion she helped her dad make which, taken before another potion, will sufficiently kill your tastebuds that you don't have to taste whatever it is you're obliged to take; Minor gets in addition to that a book about wards in general with a section on wards against lightning marked for him with a prettily handpainted bookmark.

Minor is so happy. (He got Miranda a nameplate in the style of the Supreme Mugwump of the Wizengamot, but with her name on it in her Igbo alphabet, and Karen a little glowing constellation map that can be expanded to fill half the room.)

The constellation map is so great!

(Karen got Miranda a book of healing spells, but she absentmindedly sent it by owl in advance to arrive on Christmas Day. Miranda thanks her in person anyway.)

Finis and Timothy get into an intense debate about Christmas Day and Christianity in the Roman Empire and whether Jesus was a wizard. Michael rolls his eyes and starts playing his new magical tiny violin. Aaron - who gives everybody money for holidays, and asks that everyone give him money - is helping the twins assemble a wizarding chess set. 

"If everybody gets you money and you get everybody money that seems kind of pointless," Karen remarks.

"Presents mostly serve a social function anyway," he says. "If two people get each other the same book no one thinks that's the same as if they'd just gotten themselves the book."

"It would be a funny coincidence if two people got each other the same book, it's not a funny coincidence if all gift exchanges with you in them involve money both ways. Anyway they can serve other functions."

"Oh?"

"Like, Timothy got me these quills and I didn't even know they existed and that potion Karen got everybody is her dad's secret recipe which he probably wouldn't sell you. Well, the recipe, he'd sell you the potion, but if Karen had got you money instead of her parents saying that was rude and she shouldn't do that you'd probably have got less than the potion would cost you."

"But why would she give me something that's more valuable than the amount of value she wants to give me? Also Timothy's an exception because he often knows what people want better than they themselves know it just by virtue of knowing so many people."

"Karen can get this potion cheaper than you can because her dad made it," Miranda explains. "Assuming it's useful to you it's more efficient if you get it through her."

"But she's still giving up the value I'd otherwise be paying her for the potion."

"If she sold you the potion she'd be undercutting her dad, which would have its own problems, but he doesn't mind if she gives some doses away for Christmas."

"I guess it could be a form of marketing."

"...that wasn't really my point but I guess you could think of it that way."

"I'd get someone a present if I happened to think of a thing they'd like, but I'm not good at people and it's likelier they'll be able to get themselves something that'll make them happy with the money I'd spend on them than that I'll land on it."

"Some people solve this problem by making each other presents."

"That's useful if you are unusually good at making the sort of things your friends want as presents."

"Why would you have to be unusually good at it?"

"Because otherwise you're much better off spending your time on something you are unusually good at, getting people to pay you for that, and spending the money to pay someone who is unusually good at making things that your friends want for presents!"

"...well, I hope you like the potion anyway, because my parents think giving people money for Christmas is rude."

Timothy shoots a glance at him. "It's a great potion, I am sure I'll be very glad of it. Thank you."

"You're welcome."

"But if your parents think I'm rude because I gave you money then they're stupid."

Timothy shoots a slightly more pointed glance.

"...I'll probably just tell them that you got me something you would've wanted for yourself and not be specific."