This whole concept wouldn't even be a problem if retailers didn't have to pay those fees. It's good that it serves to support the site but on the other hand it stops things from happening/being sold.
A guy I know managed to lay his hands on a batch of military boots (like 10-15 pairs) and wanted to sell them here while making 0-5$ profit just to get rid of them and allow the community to get them. He was asked to either pay to be a retailer or stop selling them.... He stopped because 50$ would make him have to lose money, it's our loss.
Another guy had the habit of buying and reselling his guns very often (always only keeping the most recent acquisition). He was asked to be a retailer or stop. He stopped selling here altogether.
Pay-per-add for a retailer status could be good. This way the "boot guy" could have paid a small fee for one ad and not be bugged. 50$/month is a lot of money for small-time or one-time retailers. It eats up smaller profits thus making selling not even worth it.
People end up selling outside of ASC on online classifieds...