Hobbit, he's asking what he should pay a mixer, not what he should charge as one.
Drewman, in my market (Vegas, non union) the going rate for something like that would be about $500/10 or $600/12 for labor only.
It's not an absolute number, but if that's what you're budgeted for, you probably won't go over.
The gear charge you'd have to work out with the mixer, depending on your needs.
HTH