Well it would stop the drive by "Nike" type spammers.
But it wouldn't stop the parasites looking for coaching victims.
$10 to answer every thread on the main forum with a loud sig file is a bargain.

The way I see it, that $10 would be a ticket of privilege for self-promotion. Like, "hey, I paid 10 bucks for my sig to be seen, my product to be endorsed and call out my clients with my lectures." Wouldn't that be harder to manage?

As I see it, there's gotta be some other way than this. Like smarter people perhaps?