There's regulations that prevent them from being undercut by entities that are willing to have transparent pricing. The problem here is not lack of regulation. It is a lack of competition. Regulation forces providers to adopt a particular business model and that model allows the kind of pricing shenanigans we see. At the end of the day everything comes down to dollars and a lack of pricing information means it is not possible to compare like services across providers. Being able to compare supposedly interchangeable goods/services is a core part of the free market and it is missing from healthcare in the US.