The issue here is very simple; unless we are talking about a single Co-Op that will have buying power approaching the buying power of the private companies than the only price difference for consumers will be the profit margins that the Co-Ops wouldn't be seeking. 

Republicans and apparently some Dems want to water this bill down so that it doesn't have much impact on consumers or the insurance companies either way but looks like they "did something" by creating several co-ops which will have little buying power and not make anywhere near enough of a dent in the cost of insurance to really be a game changer.