I voted yes. The seller/trader should be educated, find out about or they already know what they want. It's not hard to do some research and say ok sell value $350, trade value $400.
It protects buyer and seller in some ways to have the info out there and not have to go to PM's.
Even though itll probably be bad on my wallet. Nothing puts me off more than going into a thread and seeing no prices and 99% of the time I'll just close down and move on elsewhere