Earlier quoted context omitted.
In the US, someone earning $155,000 USD (Equivalent to 125k GBP) will also be paying 6.2% in social security taxes, 1.45% in medicare taxes, and then another 6.2% in social security taxes (employer's portion)[1], and 1.45% in medicare taxes (employer's portion). Added to the rest of their marginal tax rate, they'd be seeing a rate of 22 + 15.3 = 37.3%. Of course, they won't actually get health insurance for it, which…
I'm not sure where you're getting the $20,000/year healthcare spending number, but that looks like it is too high by an order of magnitude. See e.g. https://www.commonwealthfund.org/publications/issue-briefs/2... , which puts median annual household spending on healthcare between $1,500 and $5,540 in 2019. If you're talking about total annual healthcare spending, that is largely paid by employers so should be account…
Certainly not by an order of magnitude.
In the US if you are single and work for a well-funded company (e.g. FAANG types) they will probably cover 100% of the health care premiums monthly and your deductibles will be low, so a couple thousand out of pocket is realistic.
Any other scenario though, it's going to be much more. Very few companies cover all the health care costs for the family of the employee. I've paid anywhere between $1K/mo to $2K/mo for full-family coverage while employed, with the employer covering the rest (total cost is over 40K/yr).