About 12 years ago, I was transferred from Framinghan Union to Tufts by ambulance. It was a fairly routine "no lights, speeding or siren ride", with the only advanced tech being a potable cardiac monitor. The bill, paid by insurance at the asking price, was $5900. $1700 of it was mileage (at $100/mile); $900 for services not provided (probably fraud), and the remainder was the base charge..
The upside was it did not impact what I paid, except it saved me a second hospitalization deductible since transfer by ambulance did not trigger a second hispotal admit deductible.
You frequenty pay a penalty for paying direct. If you pay direct, just ask you dentist how much (s)he would have accepted from Delta Dental if you doubt this. I had a lab test (Vitamin D level) claim for $36 denied, so Quest Diagnostics demanded I pay $320. I eventually won the insurance appeal, Quest was paid the $36, and the bill was settled. The concept of "screw you" to the uninsured but can pay people is pervasive.