I'd say that's what they're getting paid now. Zero. Because there's no shortage of guys lining up for the current deal and, even if I'm sure they'd all be happy to get some extra cash (who wouldn't?) the overwhelming majority of them seem OK with it.
But what is "their market value," exactly? $10,000 a year? $50,000? $1 million?
Can you pay a starting quarterback $100,000 and his backup $10,000? If you do that and have a situation like Georgia last year, where the freshman backup takes over and leads you to a great season does it trigger a renegotiation every year?
What are offensive linemen worth and how do you justify paying them (most likely) less than the skill positions?
Do 5-star recruits warrant getting paid more than 3-star recruits? And how do you curb the inevitable corruption and graft that will arise from that subjective system that's already filled with corruption and graft.
Given the obvious difference in school budgets, how do you actually get players to go to schools in the Sun Belt Conference or MAC when they'll pay a fraction of what a Power-5 school will? And how do those small conference schools
Do you need a salary cap to ensure competitive balance within conferences?
If you're paying players a salary, do you still need to give them a scholarship? Or even require them to attend class? If not, what's the difference between the NCAA and an actual minor league? If they're only there for sports, and that's basically their job, can you fire them for poor performance or bad off-the-field conduct? If a team sucks and goes 2-9 one season, can the school cut players' pay the next?
What are the tax implications for the players?
Again, if we're talking the appearance and licensing fees that guys can earn on the side, that's something to consider. I still think there's some issues with it, but it might be workable. Same with a straight stipend that's the same for everyone. There are a lot of issues, however, with a salary system that would create a lot more problems than it solves.
The PAY THEM! crowd has good intentions, but I really think it's naive to think that will suddenly make everything perfect. Or even be a fairer system. I also wonder what they think guys should be paid on the high and low end -- a hard dollar figure you can form a budget around, not something ambiguous like "their market value." Seems like most of them think every player should be paid six figures or more, and we all know that's not the case.