Brit / American checking in and agreeing. My first startup was a B2B SaaS and hiring in the UK was fantastic - the arbitrage was just silly. Experienced software developers (10+ years) @ GBP 70k / year - and that was close to non-finance full-market pay. The same people were averaging $250k in NYC / SF.

And yet, the UK hires were often better off after all expenses than the US hires.

Largely due to housing being slightly cheaper (other posters have pointed out, London is on par with SF / NY - the big difference being London expands, NYC and SF are both "islands" - yes SF is a peninsula, but commuting up 280 or 101 is not a pleasant experienced).

Also, even offering private healthcare (BUPA) - the UK hires were cheaper. I'm in my late 30s and reasonably healthy - my all-in, gold-plated UK policy was GBP 2k / year - I was at $2,000 / month in the US.

*However* - salaries in the UK are unsustainably low.

Three reasons:
[1] BOMAD - The Bank of Mom and Dad (parents paying / lending the deposit for a house so the mortgage is at a low rate) is effectively exhausted. This means that current entrants into the housing market are either renting (which is nearly as expensive as NYC, especially after the inflationary / interest rate jump), or saving to "buy" a house (I enclose in quotes because at a 95% mortgage you don't own much of your house).
[2]
Professional salaries outside of finance are way too low. My fiancee works in a highly skilled, professional field and her salary in 2024 was, in nominal terms the same as my starting salary in NYC 17 years ago working for a large investment bank IN THE BACK OFFICE - where salaries were decidedly blue-collar. My unproven hypothesis is that the UK professional world is still largely geared towards those with alternative assets, private incomes (especially high-prestige non-professional jobs, especially around politics). This makes it impossible to compete with US venture backed startups, even post-ZIRP, because the offer is always going to be better. And yet that private-income driven base has largely been eroded through capital gains, inheritance tax and general downward social mobility (or, perhaps, less doom-and-gloom - averaging towards the center. The difference in wealth and income between the upper-middle class and the lower-middle class has narrowed significantly).
[3] There has been over the last 5-7 years significant negative messaging and tax policy against economic success. A confiscatory top-tax band, an erosion of a "job perks" friendly tax regime and a political climate that is very anti-success, even prior to the labour govt (largely started at the same time, though perhaps not by, Theresa May's 2015 speech and focus on "Just about managing").

VC in the UK is hard, largely because the majority (though by no means all) VCs are focused on aping mid-market pension managers. Their ambition is limited to businesses that already work (and yet anything transformative by definition does not work yet) - and are interested mostly in post-revenue companies with linear or lightly superlinear growth.

This, IMNSHO, is largely caused by the fact that, given state expenditure and the corp and personal tax burden, there simply isn't enough capital for US style VC - the portfolio approach requires capital to absorb failures. Most VCs here cannot afford failure.

The closest we get is the EIS / SEIS tax policy, which allows the offsetting of losses in failed businesses (by the equivalent of Accredited Investors) - as well as a friendly Cap Gains treatment of successes. But these are largely made as common stock investments by individuals - and limited to a very small scale.

Which brings me to my final point - the SAFE note is not only not ubiquitous here, it's rare. Even pre-seed investments are either common stock or (more rarely) convertible notes. This requires a level of diligence (even on small tickets) that make capital formation incredibly burdensome.

There's absolutely a path to resolving this - but the UK first has to make a political and cultural decision to embrace startup-led GDP growth, which is has not yet made.