This suggestion has been made before, that there should be separate Vendor and Trusted Vendor categories, where the Trusted Vendors pay more. I think BMR does something like that. The single, fixed high fee reduces the number of scammers, and DPR has decided his strategy is to get rid of them entirely. He doesn't want an ecosystem of mixed trusted and scammer accounts. With a $500 fee, only people who are serious about vending for the long term are likely to sign up. This precludes honest people who might have a single windfall of items they'd like to off load, but that's the trade off you make. It's an imperfect system, but right now it's vastly better than the swamp of scammers that exist on clearnet.