How many items can you sell before you should pay vendor fees?

Also worth mentioning is that the sellers that bump their ads DO pay a fee, they're Gold members (otherwise they wouldn't have bumping privileges). And I'm just guessing about who we're talking about, but the sellers with the most ads do bump them, and are gold members already. So they are paying for the the ability to bump their ads all the time.
Yes sir! Those guys also know the rules, follow them , and we as moderators don't have to babysit what they do. They title their ads in the correct heading, include necessary info like location, prices, and photos, and mark the ad sold when it is over. They are also very conscience about the 3 day bump rule. We still look them over but their "professionalism" makes our volunteer jobs much easier.