Gasoline would be a good substitute....cheaper than mineral spirits, but you would have to use it outdoors. Early on during my Navy days, one of the senior petty officers told me to get some "solvent" from the wheel well of a P-2 aircraft. Greenhorn that I was, I spent 30 minutes looking in the wheel well with no joy. Had to go back & tell him that I couldn't find the "solvent". He took me out to the plane & climbed up the wheel to show me a valve, that attached to a fuel tank line, that accessed all the "solvent" that one could possibly need.

Over the course of six years, no one ever mentioned using Avgas to clean parts, it was always referred to as "solvent!"