Charge a dollar to submit, then get it refunded back when someone reviews it and confirms that it's not obviously GPTrash? That'd be a bit of a pain, handling those refunds and managing complaints from real authors falsely-identified as spammers (and spammers correctly identified, but hoping to argue their way through). Seems like the sort of thing that'd need software to mediate so you can easily click a button to do the refunds and some third-party company fields complaints.
But then you run into the problem that such a system would cost money to build and maintain, which'd require charging Clarkesworld a fee, and they'd apparently have trouble paying that. Maybe the SaaS providing this service keeps some percentage of the dollar that submission pays that's identified as a spammer, but that sets up a terrible conflict of interest...
I dunno, it's an interesting problem. One that I'm glad I don't need to immediately solve. :S