Same, I've been mapping out CA average prices at http://hospitalprices-env.eba-r2yhwdcw.us-west-1.elasticbean...

Comparing just the price of a hip replacement is difficult, because there are so many other services that will bundled in with a hip replacement (anesthesia etc) that may not be represented in the service price alone.

The "average cost by diagnosis code a patient comes in with" transparency requirement is an attempt at solving that, but doesn't differentiate between insurance plans.

Also, I love OpenStreetMap, thanks for your work on that!