Your premise is true, but in reality it doesn't matter much who the star is. Had Denard Robinson never come to Michigan, the number of jersey sales those years would have been pretty similar, I would bet. Because instead of people buying #16, they would have bought Tate's or Devin's jersey (since one of those guys would have been the QB) or Brandon Minor or Greg Mathews or something. Sure, fans want to buy the jersey of their favorite player, but if that guy wasn't on the team, they would just have a different guy as their favorite player.
"It's a lot easier being a drug dealer than an AAU coach" - this guy. Tell me something I don't know. I mean, don't think but have never tried either.