Put it this way, vendors pay to put their stuff on the site. A LOT of plant/fish/invertebrate vendors are there. That would piss a lot of vendors off, if they keep getting cut out because someone sells shrimp babies, from shrimp that they bought off of a vendor, for a quarter less per shrimp. Cutting out the vendor, and not paying fees, you are making money doing this, and only selling at .25 less?
I don't think it's going to be that anyone will have to pay a fee, but someone selling in 'bulk', will have to. See what I am saying? Basically, if you have a one time bulk sale, you pay a small fee to be a one time vendor.