I've been pretty lucky- I mostly just buy, and every board member I've bought cards from have been excellent to deal with.
Made one trade quite awhile back and walked away very happy (thanks again Jim)- was very simple- I posted what I had to trade and what I wanted in return, was contacted by a great board member who was down for the trade and had what I was looking for- done deal. Prices of what one another paid for their cards was never a topic, for IMO it didn't matter.
I think if one half of the trading party is left feeling not so fresh, something wasn't right. Just my opinion.