Yep. And costs are truly insane in Greater London. Bay Area level housing prices and Boston level goods prices, but Mississippi or Alabama level salaries.
But that's my point - salaries are factored based on labor market demands and comparative performance of your macroeconomy (UK high finance and law salaries are comparable with the US), not CoL.
I mean, seeing an open position does not equal that position ever being filled. It can also likely be a fake position, trying to create the "we are growing and hiring!" impression, or mandated by law to be there, but made artificially worse, because they have someone internally, that they want to move to the position.