A tattoo artist can charge whatever he or she wants for a tattoo. It all varies. How well known the artist is, how big the piece is, how detailed it is, how much time will it take, etc.
Here's the thing though, this guy can look at all these tattoos and easily see any of them costing between $1,000 to $3,500. But he will most likely charge them less because they are Buckeye players and there is absolutely nothing wrong with that. Same thing with barbers. You get well known with the Buckeye players you might charge them $10 instead of $15 or $20. They can price it how they want it. The money isn't the problem. As long as they say pay $100 bucks, get the tattoo and that is that, everything is fine. It's when the conversation sways to "Hey man I'll ink this sleeve on your arm if you sign that poster" is when things can go bad. If the artist is willing to do awesome tattoos for cheaper prices to make sure all these guys on the team hear about him and how he has good deals then he continues to makes money and they keep coming. Even though you're not supposed to talk about how much you were charged by said artist anyway.
So basically, he can charge them a dollar per tattoo if that's all he is getting from them.