I'm in an IATSE house a few hours away from Chicago, and the base rate for hands here is $16hr/4hr minimum. It also depends on the position - a high rigger here starts at $24/hr for example. Some of our local hands also work in Chicago, and I know they get paid much more, but I don't know the figures. I heard one reference doing a load-out at a particular Chicago venue and it being a minimum $250 - but I don't know the per hour or how many hours it was.
When we did our contact negotiations, our research said that we were on track for cities of our size for our union payscale, even a bit high.
I’d suspect the pay variations have more to do with a theater company’s size & budget than where it’s located
A lot of it is based on local cost-of-living. As far as non-union wages, I believe that you're correct that a lot depends on the theatre's size, but when you start dealing with union contracts, a lot depends on what the local economy will support. There is no way that we could survive as a venue if our stagehand rates were similar to Chicago's, promoter's wouldn't make any money on their shows. When we were doing our research, we did a lot of cost of living comparrisons around the country to find what the going union rates were, and what was affordable with our local economy.
-Centaura