Shopkeepers normally rip you off blind, and you usually get angry 'cause of that.
Here's a way to get everything you want from a shopkeeper, and have more money than you started with.
1) Shopkeeper must have 2 similar items with different conditions.
2) Buy the cheaper of the 2 items.
3) Sell it back
4) Do this several times, because after about the 2nd or 3rd time, when you start buying it back, it will either have max repair, or 1/2 condition.
5) When you sell it back, it should earn you more money than you payed, 'cause if you aren't selling it back for more money than you bought, you're still getting ripped off.