I don't think this is about whether Tebow is good enough or not. It is a pure business decision and it tells you that there is money to be made for minor league owners as well as major league owners. Assume Tebow's 100k bonus and amortize that over 70 home minor league games which is about $1500 per game. Assume the average minor league ticket is 10.00. Tebow only needs to bring in an extra 150 people per game to break even and that does not include all the money they will make off of concessions associated with the 150/game.
I am guessing that all minor league owners already know how much revenue increased when Michael Jordan played for example, and they have used that information to factor in Tebow who - although not quite as big a name as Jordan, is still a very big name nonetheless. It doesn't seem a stretch at all to me to believe that Tebow will draw well over 150 people per game over what they would have gotten without him on the roster.