I guess the main countervailing force against this would be pricing pressure from employers looking for better deals. I don't really know what the power balance

I guess the main countervailing force against this would be pricing pressure from employers looking for better deals. I don't really know what the power balance looks like in those negotiations, but employers banding together would certainly tip the scales It is my underatanding however that a lot of providers have payers under their thumb. A great example of this is the UCLA vs blue shield (or blue cross?) of CA a few years back. Another commenter here mentioned UPMC, another example of a mammoth local provider dictating what payers do. Sutter health in the Bay Area is a similar Goliath, and the publicly traded hospital systems (community health, HCA, etc) have made a business model out of exploiting local hospital monopolies to extract money from payers. Payers definitely don't like this, and if they start getting squeezed on the other side from employers, it could really squeeze some payers