"Cash pay only" doctors compete with the existing system today. With the rising upfront costs each year, there's an increasing trend of a cash pay doctor's office visit being cheaper than the co-pay of your insurance provider.

Why this is true a separate discussion (possibly overhead of dealing with the healthcare system or insurer).

We have seen that trend of more and more cash-pay only physicians and think it is great!

Ultimately more transparency leads to more competition which leads to lower costs.

Not necessarily when the choices are constrained by the health insurer. We (a big VC funded primary care provider) experimented with full transparency pricing. Never moved the needle. But that was 10 years ago so maybe things are different now.

Agreed, insurance companies are typically a big cog in the wheel. We're starting to see things change as high deductible health plans have grown so rapidly. The consumerism of healthcare is starting to create change (i.e. price transparency executive order signed in June).