I'm going to say what I'm positive others are thinking.
Would I do it for free? Hell no. Put up with whiney players (adult league) or obnoxious parents (youth... and adult league) without something for my efforts? Not on your life.
Is it about the money? No. Don't confuse "wanting a little something for my troubles" with "money, money, money." Gas prices are high. I have a mortgage. I'm away from my wife.
Have I or would I volunteer now and then? Absolutely. My first 4 years behind the plate were actually spent volunteering for local kids' games - kids that could otherwise be hanging around in the streets and getting into trouble. I certainly enjoy calling ball, and if the group is a good group, I'll gladly do it.
But if my assignor asked me to call ball for free for a month, I'd tell him he's nucking futs!