BP has publicly committed to pay the actual clean-up costs (and I'm just gonna keep on breathin' while I wait for THAT to play out), which will amount to $$$ BILLIONS! it's true, I just watched a BP spokesman on TV say so.
BUT... (there's ALWAYS a but - and this is a BIG one), federal law caps their consequential damages liability at $75 MILLION!!! Businesses, families, workers and governments depend, directly and indirectly, on the Gulf's rich biological diversity and environmental beauty for their livelihoods. And that's GONE! Those costs will far exceed the costs of the clean-up itself (see Prudhoe Bay, Exxon Valdez for further information), and there's no real help out there. The SCOTUS precedent on the Valdez basically set a standard no one could meet anyway.
The greatest costs are going to be borne by those least able to afford them... the folks who work the Gulf for a living, and the businesses and governments that depend on them.