agree with all, there was no way I would waste my effort for his offer. For a mix only with no gear I charge more than that. granted, my set up is small (very similar to yours), I got rid of the big boxes a few years ago.
Set up would be 1/2 hour since everything is prewired and color coded.
on the other hand, there are other people that are friends that I will mix for free as long as I don't have to haul stuff. chances are I'm going out to see them anyway and rather than complain about the mix, I will help out. usually it leads to more paid jobs. But a person I don't know, hauling gear for a first gig with some potential of additional work is not worth less than $200.
in this area they can get it for less with some of the local hacks or even rent the gear for $100.00 for the night.