It's probably less than fifty cents. Naturally, it depends on the efficiency of your stove and crock pot, whether you have a gas or electric stove, whether a gas stove has an electric igniter, the relative prices of electricity and gas, etc. Also, running a stove at 200 requires less energy than running it at higher temperatures. You are correct that the crock pot is cheaper to run, but the difference isn't so much that it should influence which appliance you use (unless you are doing this every day!).