You don’t have to be a “high earner” to leave the UK, or America for that matter.
I left the UK 25 years ago with under a 1,000 dollars, and haven’t looked back ( that doesn’t mean I don’t love my country, or my family).
I left 20 years ago, I checked on one of those friends re-united web sites and about 1/4 of the people i knew on it had left the UK as well.