The real financial decision isn't on price comparison, but rather whether or not to get the treatment at all. I made a cost-based decision on treatment a while back. I was being treated for an eye problem where I was at risk of permanent blindness in my right eye. Treatment involved monthly injections of a quite inexpensive drug (about $27 iirc), that was inexpensive because it was developed for other, more common conditions and had been around for a long time. My doctor wanted to try a new, specialized drug, hoping for better results. It cost $8000 a dose. With 90% coverage, I would have been paying $800/mo out of pocket. I decided to stick with the cheap drug that seemed to be working.
But that's the sort of cost difference that matters, not the "This doctor is 5% cheaper!" dream of idealized free markets.