... Now for what I am thinking about doing...
A few thoughts:
• Thanks for removing the requirement to use Panjo. And I'm not sure whether Panjo required the use of PayPal (I haven't posted an item for sale recently), but I also hope we never have to use PayPal.
• The solution to the bumping problem suggested by many people (and the one I, too, like) is to have only posts by the OP (after some period of time) move the thread back to the top of the list of threads. In another thread you said "it is not doable easily in our forum software." So I read that as meaning that it could be done, but not without considerable effort. Perhaps, then, this could be a longer-term solution -- something you can't easily do now but could accomplish with some effort. I just don't like the easy solution of allowing only the OP to post in his thread. A lot of useful information has been posted in sales threads by other members than the OP. Expecting any such useful information to be posted by the OP if it is sent to him in a PM isn't realistic. A medium like newspaper classified ads does not allow for public comments, questions, etc. But an internet sales forum does make such posts possible, and I think they can serve useful purposes.
So if you continued to allow all posts to bump up the thread, how could "bump scamming" be better controlled? More focused moderation of this situation, with warnings and then bannings would do it, but that would require more time by the moderator(s). I have seen some people offering to help; would you be willing to add moderator(s) to do this? Perhaps asking for ideas from other members on this point would produce something else that would be useful. I'd actually rather continue to have "bump scamming" than to eliminate all posts by anyone except the OP.
• I like the idea of limiting the number of threads a member can start in x days, but I think 20 in 30 days is way too many. That's conducting a business. You mentioned the possibility of creating a "business member" account type; I'd think more than a few sales threads a month would throw someone into that category.
Alternatively, instead of limiting the number of threads that can be started in x days, how about a limit on the number that can be active at any one time. That would require some sort of indicator on the thread for the OP to be able to throw it into an archive (with additional posts no longer bumping it up) and remove it from the threads that count toward the limit on active threads. But if the item sold quickly, the OP could then always start another thread right away rather than waiting for some time period to expire.
• As for subforums, I'd like to avoid that as much as possible, whether by price or type of merchandise. I kind of like the "open bazaar" nature of what this forum has been. However, if you do it in some fashion, I'd suggest something like: (1) Cues Under $1,000, (2) Cues $1,000 and Over, (3) Cases, and (4) All Pool/Billiards Services and Equipment Other than Cues and Cases.