In the US I phoned my insurance company, got an Uber down the road to the hospital, and walked in passed the (armed?) guards to sit in a crowded waiting room. Receptionists took my blood pressure twice, was unimpressed with my (international) insurance. 2 hours later I went into some form of casualty area and sat in a chair, had blood pressure taken a couple more times. Eventually someone came and gave me a tablet, then they wheeled in some computer trolley to take my credit card (about $900), and gave me a prescription. There was no informing me of prices up front, no choices (not that you have much of a choice when you're in hospital - for me it was a really minor thing so I actually would have had the choice to either pay or not pay).
A few weeks later at home I received another bill for $2k from the hospital. I believe the bill charged for each of the times they took my blood pressure, I was never asked "would you like your blood pressure taken for $200", I wasn't asked if I wanted to sit in the comfy chair rather than the plastic chair for an extra two slips of latinum, the price wasn't up for negotiation, it just was.
The difference between the two cases is night and day, the UK treatment is fast and free, the US will make you wait for hours and then charge you a fortune.