Curious if that is actually true when comparing to tier 1 banks/hedge funds full time employee salaries+bonus+retirement+healthcare.
Assume 600 GBP/day * 22 day/month * 10 months (realistically) full time work, that's 132k/yr.
From that take out accounting, illness, insurance, healthcare, retirement, travel, possibly more.
All things considered, once you get above 100k base as employee contracting becomes less attractive.
Strictly as a money move that is, there's other dimensions for sure.
Ie. 900+GBP/day is listed rarely and for very specific/niche things.
Then, the more niche it is the more likely it is that the downtime between contracts becomes longer I imagine.
Curious what your anecdotal experience has been, to the extent that it can be shared.