Should I hold them to the price?

Come back and let us know if you get any type of "Thanks" from the seller. My bet is that you won't.
A seller that made an honest mistake will thank you for what you did. A dishonest one will just smile and move on.
You're a good guy for what you did.
I wonder if the seller would appreciate knowing about this thread, filled with so many people sharing the angst of trying to figure out what's "right"? An honest seller would. I don't know what impact it would have on the other kind, and I see no benefit to spinning my wheels guessing about it. Moving on is often the noble choice.

Nice to see all the support. Thanks for displaying some Christmas spirit; whether it was deserved or not makes little difference in its reflection on those who do it.

- Erik

64 Valiant, 170 3-spd
82 Volvo wagon, 5.0 5-spd :)