2300 isn't that expensive BUPA would cost you nearly double also please don't compare the public healthcare spending it has nothing to do with the actual prices you end up paying.
The health care expenditure in the US is the biggest in the world but that's including all the prices that insurance companies pay for treatment and services.
If the US stops charging 3000$ for an MRI scan it's expenditure will go down drastically (an MRI costs about 300$ in most European countries) but it might not have any affect on what the individual ends up paying.
I last looked about 6 years ago, right enough, but then £120 a month was the maximum charge I could find, that was with zero excess and get paid money for any nights in an NHS hospital, etc etc. I'm not sure what I'd need to add on to get it up to £200 a month - a free chauffeur for any time spent sick? ;-)
I suppose prices could have increased a fair bit since then. Also, I note you're in London. I'm in Scotland, so we actually have a different NHS, and it does generally get rated higher than NHS England.
I can compare public healthcare spending as that's the money that comes out of your taxes. Americans are taxed more for their public healthcare than we are in the UK for the NHS. They also pay more for private healthcare than we do in the UK. So your claim that it's more expensive here is simply wrong.
The health care expenditure in the US is the biggest in the world but that's including all the prices that insurance companies pay for treatment and services. If the US stops charging 3000$ for an MRI scan it's expenditure will go down drastically (an MRI costs about 300$ in most European countries) but it might not have any affect on what the individual ends up paying.