As with Beckham, I would think that Rodriguez earns his 20 million in advertising, image rights, appearances, etc., rather than earning 20 mil + the add-ons.
As for Chelsea players being on 68K, that may be true for some but I was under the impression there were 2-4 (or more) players earning 120K a week...or close to it.
Think that's the average
I'd imagine a few on 30-40k a week will bring the average down quite a bit.