Once the game has a huge number of players, someone will make www.plprices.com and automatically update it with scripting. ie. issue searches via scripting, screen capture, and update the database. There may be a way to do it without violating the ULA.

If the game has enough players, then such sites will start popping up. Also, www.plmaps.com, www.plquests.com, www.plguilds.com, etc.