It's simple really. Not even Sampras could play with that log Wilson made. Really, it's surprising, but Sampras got more from Babolat than Wilson in his heyday. From what I understand, Sampras got $0 for using the ProStaff. Babolat gave him free gut, I'm not sure about the $'s accompanying but the way he went through gut it wouldn't surprise me if he just got free gut.