Sorry, I'm not going to Google "cheap MRIs near me" when I'm bleeding out on the floor having an emergency. Healthcare is not expensive because you can't see how much a doctor visit costs, it's expensive because that's how a lot of people make a lot of money, and they get very upset when that is threatened.
Most medical care is not an immediate emergency. If I could compare MRI prices and it would impact how much I pay (either as an insurance copay or out of pocket) I would absolutely do that. But I have no opportunity to do that so there is not price feedback like there is in a market.