Sold Crafted Items Pricing
 

I haven't noticed it with other items specifically, but definitely when I try to buy sold crafted arrows off merchants everywhere. The arrow's would cost around 3 silver each, and when the first stack is bought I am charged the proper amount. However after that, the merchant NPC changes the price to around 2 gold per arrow. It resets after you exit and reopen the merchant window with the NPC.

I haven't noticed them doing this with the other items i've bought, only arrows, so I don't know if this effects anything else.