Clearly the pay isn't enough to make you jump at it. Why not try pushing them on the money? Not much, just some. Maybe 5-10%. If they budge then you know it's not a fixed budget, they need the help, and you can push a little harder next time and the time after that etc.
Be reliable, in a good mood, thank them for the job at the end but never ask for more work. Negotiations open with them asking you.