This analysis from the LA Times:
As for that U.N. resolution, it’s more a matter of "Let’s you and him fight." The U.S. will be expected to do the heavy lifting. And if the U.S. had been opposed, it would not be happening.
So the “you” is the U.S. and the “him” is Libya. Part of the heavy lifting is who does what. Another part is who pays.
The Federation of American Scientists say the average unit cost of a Tomahawk missile is about $1.4 million. And Danger Room reports, 122 have been launched. That’s about $170 million dollars just for Tomahawk replenishment.
Chances are that’s just a fraction of the total monetary cost only a couple of days into the Libya conflict (or whatever it is), but it’s indicative of the reality of the situation: the U.S. leads (and pays); others follow.