I have tried a different tack.

One of my two characters has bartering

Start by selling an expensive item to the vendor and NOT charge any gold for it. It instantly raises his attitude towards you to a 100.

That helps a lot.

Neither of my wife's two characters have bartering as a learned skill, but she has items that helps.

And we both sell and buy. My better prices is an option. Not a fixed rule of the game. I can imagine my wife if I told her, that she couldn't do buying or selling...
I'm sure she would make it a point to sell at crap prices all the time, until I found a common ground.
(Usually easy enough. I like sex. She likes to be right).

And to OP...
If you are frustrated by the way it is done in your game at the moment.
Change it. Play as you feel right.
Your joy should not be ruined because of a price difference of a few gold pieces.

Seems one of your players have way more power over your gameplay than is nessessary.

Last edited by Ayath The Loafer; 28/01/18 02:16 PM.

Great last words.

Oh no. Not again...