However day rates in excess of £500 are normal outside of London (£750 in London) so if you can deal with all that it can be lucrative.
Of course that depends on the type of work you do, your skill and experience level, and the type of client you work with.
In the UK what that day rate is worth also depends on whether you are working inside or outside IR35 and if inside whether you're working through an umbrella company or the client is paying their own taxes. Your £750 and your friend's £750 might give you very different amounts of real money left after taxes and costs.
Of course that depends on the type of work you do, your skill and experience level, and the type of client you work with.
In the UK what that day rate is worth also depends on whether you are working inside or outside IR35 and if inside whether you're working through an umbrella company or the client is paying their own taxes. Your £750 and your friend's £750 might give you very different amounts of real money left after taxes and costs.