GB was thinking very hard :
I've just fitted a new tap to our kitchen sink. It took me nearly 4 hours.
That did include altering the pipework. Plus puzzling over the instructions
on the rather complicated Bristan Easyfit tap. Great taps, awful
instructions.

But 4 hours! I'd expect to pay a plumber no more than £100-150, and that
might well include coming to quote first.

A tradesman will (should) have all the tools to hand and have the
experience of what is involved to make the job much faster.