You could not pay me enuff to go up the
mast to perform anything.
As has been pointed out above, this is a high risk
project for anybody.
I'm assuming the rigger must drive from somewhere, so there is time and distance to get to your
boat.
Then he has to sort out how he is going to get up there.
Once up there, he will be required to do some work, so he'll have to prepare a toolbag with all the correct and required tools.
He may even have to come down again, and go up again, for any number of reasons.
Once done, it's everything in reverse.
Realistically speaking, this could be ....for him...a 3-4 hour
project all in all, so the #375 does not sound totally unreasonable to me..