If the law were serious about medical price transparency, it would just state that no medical bills are valid or enforceable in any court unless the exact price is clearly disclosed to the customer and agreed upon up front. Without relying on any government enforcement, we'd see an end to surprise billing overnight.
Business practices would have to change. In cases where the all the steps and treatments aren't knowable up front, providers would have to pick a price and stick to it - like any business or service provider they'd make money on some and lose money on others. Instead of issuing separate random bills from various providers, hospitals would have to pay their subcontractors out of their fixed prices, like a normal business. There may be exceptions for emergency care but those would be the rare exception, not the rule.