You are equating higher cost with better quality. There usually is a correlation, but with US healthcare's opaqueness with prices, I wouldn't make that correlation.
Leaving aside that, people do in fact make medical decisions based on cost. For example, for angioplasty there are two options - a medicated stent and a non-medicated, regular stent. The medicated stent is more expensive than the normal one. When it came to choosing one for my father, I chose a medicated one only because I was paying through insurance. But many of the patients out here in India don't have insurance. In that case there is a definite probability that a lower cost one will be chosen. Another example is dialysis. The frequency at which people perform dialysis is directly related to cost and affordability.
It is not always a given that patients would go for the absolute best.