What item do you own that has an unexpectedly high value?
This could be something that you bought for a higher price than what most people would guess based on the item, or it could be something you bought for a normal price that has gained significant value as time has gone on.
What made me think of this question is a LEGO minifigure I got with my "The Hobbit: An Unexpected Journey" disc. It is Bilbo Baggins in a blue coat that was apparently only sold in that movie box only at Target stores. Even considering the exclusivity, I would have guessed maybe $10-20 for such a tiny piece of plastic, but there are sold listings on eBay from $80 to $225. I could possibly even get towards the higher end of that number since I still have everything in the original box in good condition. It's not worth a ton compared to some other items people may own, but I think most people would not expect nearly that amount.
I own a full size Batmobile model from a canceled game bundle Batman Arkham Knight: Batmobile Edition. It was canceled due to quality control issue and was shipped to select people before getting canceled. So that's a pretty rare find. All the electronics still works and it can switch normal and battle modes with a remote. Had some people offering multiple thousand bucks for it, and I got it just randomly without knowing it's rare.