I think that the issue really may be just the balance billing. Since it has the capacity to significantly increase your out of pocket bill.
http://www.forbes.com/sites/christinalamontagne/2015/01/26/what-is-balance-billing/
"In your case, your provider charged $2,076 for your services. Though your health insurance policy covers 50% for out-of-network care, this 50% is limited by how much they allow for each service. Looking at the numbers you gave me, it appears as if your insurance company only allowed $800 for the services you received. They paid half of this, $400, and the remaining $1,676 is your responsibility.
The specialist you saw is now stuck with an unpaid balance of $1,676, a balance for which he is free to bill you."
The maximum that the insurance company is willing to pay for out-of-network costs is a number set by the insurance company. I'm making these numbers up - for heart attack treatment, say that the maximum out-of-network your insurance company will pay is $15,000. The hospital decides to charge $90,000, because... it can. That's nothing stopping it. The ACA doesn't actually stipulate maximum amounts that hospitals can charge.
You then have a balance-bill of $75,000 - and it's all on you.