Because Pedro actually proved himself as a vital part of this team before his from dropped in the last two years. Something that Alexis barely managed to do since his arrival. And Pedro didn't cost 37 fucking millions at the first place. Pedro keep his head down and try to play his game rather than keep falling down like a lousy diver or bitch to the referees all the time.
Pedro is off-form. Not a misfit, like the other guy.
Yeah, a misfit player outscored Pedro last season even tho he played less
Also, Alexis seems to get himself into scoring positions much more often than Pedro thus making him a bigger goalthreat. Dude just needs to finish off the chances he gets...
The price Barcelona paid reflects how awesome Alexis is. Several top clubs in europe were hunting him but he chose Barcelona. It is not exactly his fault that he doesent get to play to his strengths here and yet he's been producing at least as good as Pedro.