Well fuck, the other bills posted here make me feel a little better about my own.
I think my place also suffers from the shitty-insulated old house syndrome too, though. During the mid afternoon, some of the back rooms which were added on to the house heat up VERY fast compared to the main part where the living, dining, and kitchen room is, suggesting that insulation is nonexistant where the two bedrooms are. We tried getting solar curtains but that helped very minimally.
I think I'm gonna give that measuring thing from newegg a go, so I can see what exactly is so demanding on our bill. It's most likely the AC, but it's worth seeing what else is doin it.