it's actually a little more nuanced than that.
Hospitals/providers have what they call charge master. it is probably the cash price you are mentioning.
Even uninsured can end up negotiating the bill, albeit after the fact.
Sometimes, insurance might negotiate lower prices than what a certain procedure/treatment costs, i believe that's not uncommon. They make up for it from other procedures in general.
1. The lack of health care cost transparency reduces price competition.
2. people not asking for price in advance, or not caring because the are already past their 1. deductible 2. out of pocket maximum makes healthcare expensive[a]. Similar to reference pricing, high-deductible health plans (with added HSA benefit) makes people think twice before going to doctors. I also felt a lot of people are not price conscious about healthcare - just yesterday a friend mentioned "i picked the most expensive plan so i don't have to think about it". Completely reasonable, but one reason why prices get higher each year.
[a: reference pricing] http://www.nytimes.com/2016/08/09/upshot/how-common-procedur...