I used to like the PB buy/sell but lately I just get frustrated as every bike/part seems to be listed at roughly the online sale price, or what your LBS would ask for a new bike if they had one sitting around from last year. No doubt every seller looks around and anchors their price to what others are asking, and inevitably a ton of haggling has to take place before a deal can be made.
If sellers could put in the price when they mark a product sold, and future sellers could use THAT as a reference, it might bring some sanity to the process.