The way it was explained to me by my Human Resources Department is that when individuals go through a large corporation for their coverage, even though the Aetna's and Cigna's give the companies "bulk pricing," the company still eats the majority of it. For example... My health benefits cost me $70 a pay period for a fully comprehensive plan... Single, healthy male, 38 years old, not married, no kids. In addition to my $140 a month, the company would pay Cigna another $250 for me per month, totalling almost $400 a month. So all in all, I guess it would be similar as if I had gone to the marketplace and chosen one of these $400/$500 plans a month. Or maybe not?
Truth is, these providers look the other way with major corporations because there is a risk that the company may decide to take all of their business to another provider. I've been with my company 8 years now, and in that time, we went from Aetna to Blue Cross, then to Cigna. So take 9,000 US employee plans + spouses + children/dependants, and yes, they will look the other way on certain things. Someone choosing an individual plan I'm thinking it's easier to deny coverage, because it's just one policy at risk. Makes sense? (It's late.)