Here is an additional piece of information not mentioned here yet: The Lakers gain TWO trade exceptions in this deal.
They gain a trade exception for the difference in salary between Gasol and CP3 (about $2.5 million) and another exception for Odom's salary ($8.9 million).
They are trading away about $27 million and acquiring only $16 million, so they get $11 million in trade exceptions.
That $8.9 million trade exception can be used to acquire a very good starting power forward.