My situ.: 3,200 sq.ft., 2 A/C's (One 5 ton & One 3 ton, both 14 seer), home is just over 3 years old. Last months bill was $148.00 (2,022 kWh). The key is that I am on the "Time of Use" plan. Peak charges occur between 1pm and 8pm. Mine is set for 77 at night (off peak), 84 during peak hours. The key I think is that I really cool the house down prior to on peak hours to ~69 degrees, and the unit doesn't need to come on till about 6:30pm, and it only stays at the uncomfortable 84 for about an hour and a 1/2.

You definately have a problem here. Hell, I mean I live in Hell .

1) Ensure that your filters are new and/or clean
2) Get on a time of use plan and get/use a programmable thermostat
3) Close blinds/curtains during the day
4) Install sunscreens on major exposed windows (This is a must here in AZ)
5) Check temperature differential between indoor ambient air temp and air temp coming directly out of your registers. The differential should be AT LEAST 18-20 degrees. If the differential is less than that, then you probably need a freon re-charge.
6) Have A/C coil checked and cleaned

How many A/C units do you have, and what size unit(s) do you have? It is quite possible that your unit is overloaded due to the size of your home i.e. I have 8 tons capacity for 3,200 sq.ft. You will know it is overloaded if it is continuously running and never seems to shut off.

That's all I can think of for right now.

Oh, check with a couple of your neighbors to see what their bill is running and/or call your Electric company to see if they can do a comparative check for you.