Would you say the same about Usain Bolt because he doesn't run marathons? His talent is also the 'short-game" of the sprints!
Mills is a professional, and therefore should try and get the best deals for his talent. He is limited to 20/20s and therefore has to play for many teams. He would have played in the IPL for much less than 1.4 million, but who in their right mind is going to turn it down when the team bid that amount for him. Is he going to say, oh that is too much, pay me less?
It is not his fault and good luck to him.