There is a somewhat hidden jewelry shop in the city of Phlan. It's coordinates are (8,10) and you get to it by going into a normal shop and then heading through the back door.
I found a bug in this shop. Either that, or a the jeweller is crooked.
I had a pile of gems and jewelry to get appraised. I took it into the shop, pooled my cash, had one character take the gems and jewelry and then had them appraised. After all the appraising, the pool of cash was 15000 platinum pieces. (In this game 1 platinum is worth 5 gold. I'll use pp and gp to refer to platinum and gold pieces, respectively.)
Since I couldn't actually carry 15000pp, I had one character buy a trinket worth 75gp. I wanted to see how bad I lost cash by buying one small, light item worth a lot of money, and later reselling it when I needed money.
When I checked my pool of cash again, it had dropped from 15000pp to 1400pp!
Bug or feature?