There's lots of ways that market forces that should normally work don't. For instance:

* the amount billed to individuals is often wildly different than the bill an insurance agency would negotiate with a provider. (I'm not an expert, there may be more layers of indirection there; this is simply my mildly-educated impression.)

* Depending on the sort of care you seek, a provider may have a de-facto monopoly in the area.

* There's no obligation (or indeed incentive) to be up-front about costs—we've all had the experience where we were charged for a service that wasn't even presented as a clear option, let alone one that would cost money, let alone anything approaching a reasonable charge for the service rendered.

* When you need care the most is often when you're least able or inclined to play providers against each other/shop around.

* Deductibles are so high we're essentially pitting high regular premiums against worst-case scenarios, which is deviously difficult to reason about, even for actuarial experts.

...etc etc. It's not easy to proactively think through costs in the world of American healthcare even as a cost-conscious, pessimistic actor. And on top of all this, the sheer bureaucracy necessary to manage negotiating payments and insurance coding adds a significant amount of overhead (inefficiency) to the provider's end bill and to your premiums—how on earth can you audit a provider's or insurer's efficiency? It's all opaque, and most of us don't want to think about it at all.