I did a quick calculation for you. With the items you listed you should be using approximately 322 kWh for 31 days of operation. I calculated with you running your 6105s at 100% though.
I used the rates listed on the BC Hydro website (
https://www.bchydro.com/youraccount/content/residential_rates.jsp) but I am not sure if they are accurate. I live in Calgary.
322 kWh x $0.0667 / kWh = $21.49 / month (if your total household electricity usage is < 1350 kWh / month. If you are over that amount the amount above is charged at $0.0962 / kWh
As Aquattro mention check your exact rates on your bill. It probably something else that is causing it (fridge, freezer, etc).
Hope this helps.