Lol okay Rooon, I'll simplify. The only way what you say could make sense is if somehow Tevez's purchase increased your fan base by X amount who all by his shirt giving you an extra £20mil. I think it's naive to think that Tevez has that kind of fan base who follow him.
Only the big players like Beckham, Henry, Ronaldinho etc. can have the "£20mil effect." And maybe Park Ji Sung or other Asian players.
Its quite ignorant to believe that over the next 2 years Tevez is going to bring in anywhere near that amount.