I would say the Phone Exchange forum is just a place to buy and sell items, with minimal to no discussion on what people are charging. You can "open a can of worms" when trying to figure out why someone thinks someone else is charging too much for a given item. It keeps it cleaner when someone posts to sell something, then someone responds looking to buy the item.

I have seen also seen threads in that forum degrade into an argument on why some people think a seller is asking too much money for whatever items they're selling.
If you were to post questions on what items sell for in general, I think the "7-Eleven Rates and Plans" forum might be better, after all, the caption under it says"How much you pay for what, etc."