I used to work in health insurance business, and actually a lot of this information is available via CMS: https://www.cms.gov/Research-Statistics-Data-and-Systems/Sta...

It's mandated in a sense because all Medicare data has to be sent to and aggregated by CMS and then reported on. So I think this already happens.

California also has some mandates about hospital "chargemaster" data, and the data is publicly available here: https://www.oshpd.ca.gov/chargemaster/