So I'm a British ex-pat in California, been out here on/off for past 5 yrs, past 3 of which I've been a legal permanent resident. Prior to 3 yrs ago, I was living/working in London for 10 yrs.
here's my take:
i miss the NHS a LOT- as someone pointed out, it's not perfect, but it is there, it doesn't involve insurance companies, it doesn't create an environment of discrimination against lower income groups and it's a safety net. i usually describe british healthcare to people over here in the US as an entitlement rather than an essential luxury.
it's not only co-pays (the same as an insurance 'excess' in the UK) that add up, but also the prescriptions, the price of which varies according to the drug. we've had 3 prescriptions in the past year that we haven't filled because each one individually would have cost close to $100 (even after our insurance contributions and we're supposed to have 'good' insurance). that includes childrens' prescriptions too- they're not free over here like they are in the UK. And senior citizens do not get free prescriptions either- our neighbour (before his hip surgery last summer) had been paying $800/month for two years for generic (non-branded) drugs on top of what his insurance covered. and that was just to give him a bearable quality of life. my FIL thought it was great how he was 'only' paying $3000/yr for my MIL's anti-depressants. the whole healthcare system over here is one of the hardest things that i've had to adjust to as an expat over here. i curse the system each time we have to use it and have an emergency budget set aside ever since all three of us had to visit the doctor in one week last year and those visits ($20 co-pay each) plus one 'tiny' prescription ($70) cost more than our weekly food budget. and i'm still disappointed that when we changed insurance last year (my husband's company no longer chose to subsidise our provider) we had to switch all our doctors and it meant that i had to wait to start the process to get our son speech therapy as he had to go through all the assessments with the new insurance company.
as for schools, yes they do vary from place-to-place. we are in california which overall has terrible schools (and getting worse), yet there are certain school districts here which rank in the highest in the country. but unless you're in those areas, most people like to go the private way. in the good school areas, housing costs a LOT so either way you're spending out a lot for education, be it for the publicly-funded 'good' schools in the uber-expensive property areas, or for the uber-expensive private schools. American education seems to be a lot more general compared to UK schools where we specialise in things a lot earlier and the UK education is more highly regarded at the primary-secondary-bachelor's degree level (american children usually have to catch up when they move to british schools), but at graduate school level, the reverse is true...more likely as a result of the more general background knowledge (plus longer degree courses), and so the brits tend to lag behind when it comes to calibre of Masters and PhD students.
on the subject...college is also super expensive. things are changing in the UK, but you can still get an entire undergraduate degree from Oxford/Cambridge for less than the cost of one year at Harvard. Also, you have to pay fees up-front here, so if you take out loans to do it, you start getting charged interest on the loans from day one of classes (unlike in the UK where you pay the fees only after you leave, and only when you're earning over a certain amount, and they write your debt off if after 10 years you still don't earn enough).
property tax is similar to council tax, but you don't get as much for your money and it's a lot more than what my parents' pay back at home for their council tax. we pay about $500/mth which is considered to be low for the area (as we live in a 'cheap' house which is still insanely expensive to me but we live in the Bay Area). But that does not include things like garbage collection which is contracted out to the private sector and in some towns near to us (fortunately not ours) does not incude fire service, where you have to pay a kind of 'fire tax' otherwise they will not respond to a call-out. similarly in some areas here if you get into a road accident 'out-of-area' you have to pay for the emergency vehicles to come unless you take out the insurance for it.
in addition to income tax and property tax theres also Social Security to be paid on each paycheck which is proportionately about the same as National Insurance, except of course it doesn't include the medical...which as you've gathered adds up to a lot.
although certain material things cost less (cheaper electronics, cheaper petrol etc), certain things are more expensive (clothes, milk- yes I pay $6/gallon here too!) and wow, baby/childrens' items and toys are a LOT more. diapers are TWICE the price of the UK, baby milk cost FOUR TIMES as much. there is no tax relief on childrens' items either. and magazines, they're also a lot more too for some reason (unless you take out a subscription which makes them dirt cheap). books are also more expensive and there are no price wars between booksellers/supermarkets to slash the prices down (which i presume is why the food costs more here too- no supermarket price wars).
eating out may seem cheaper on the menu, but when you include the 20% tip, and the 9% tax, really it's not that cheap after all. Mobile phone plans are also 1.5-2x more expensive. cable tv and internet are also much more expensive (we don't actually have cable or cell phone contracts to try and save money).
Petrol is 4x cheaper, but we have to drive 4x further to get to places so it all evens out. electricity....well we use more as it gets >90/100F (35-40C) here in the summer so we have to run the air conditioning or our lives are miserable.
so at the end of the day, i completely agree with whoever stated above: although the salaries may seem higher, we don't have much disposable income by the time we have paid out all the hidden taxes and extras.
it of course varies as to where you live (we happen to live in an expensive part) and also depends a lot on the 'package' that your employer offers with regard to insurance etc, all the better if you get that whole ex-pat package that subsidises education too. my husband is american, so we just live here 'normally' without any of those ex-pat perks.
i would say my standard of living is probably higher over here- our 'small' ie 'starter' home is much more spacious than that which we could buy over in the UK and we are a two-car family on one income (but that is more of a necessity as there is precious little public transport in the suburbs where we live), but i wouldn't say my quality of life has improved... if anything it is much less. but that's because i'm the sort of person who values education and healthcare rather than material possessions. a friend of mine from germany who has been out here longer than me vows never ever to leave because she likes having a big house which is something that she would not have had back in germany. we're all different.
and obviously my experience is only in the Bay Area, it could of course be different elsewhere.