These out-of-network bills have successfully been challenged and a law passed to address them in NY (https://www.dfs.ny.gov/insurance/health/OON_guidance.htm; I think).

But, in the first place, these bills were never really valid: in no other market am I informed of the cost after I have received services. This fact is why the law was passed, though it shouldn't need to have been passed. The "contract" is already unenforceable.