And that next +$250,000 will always be there for him to earn—he can do a few extra local radio ads and eventually make it up, if he's really that concerned. The only truly non-renewable resource he's got is time, and to someone interested in an education for the education's sake—which I think is at least part of what's going on here—then there certainly IS quite the difference between settling down to study now, and doing that studying seven years from now. "At least I'm making tons of dough!" won't comfort him if he's truly interested in cultivating his mind/intellect/character, I'm guessing.
I don't think we should dismiss what he's doing as "largely symbolic". . . refusing to return to his studies until after his NFL career would itself be symbolic, too, just not as noticeable or remarkable. . . .
ps., I think making him responsible for the fate of money he has chosen not to earn is silly - should a person never have any kind of hobby, or any time-consuming endeavors that don't directly bring in $$$? If I want to start skydiving on a regular basis—if skydiving is somehow really important to me—, should I deny myself that, and instead give the $ needed to hire a pilot to some "business on the brink of closing?"