Last winter my "long" stay in Calis cost me appx £1,000 per month taking everything into consideration inc. flights to/fro.
I rented a 2 bed mid floor apartment, had the heating on when necessary, shopped at the market for fruit/veg & local supermarkets (Bim, Genpa, Tansas, Kipa etc.) for the rest, ate eat out slightly more than average (even if it was only a pide for lunch), hired a car for 2 weeks to do some sightseeing & thoroughly enjoyed my stay.
1 extra I don't see mentioned is the cost of your residency, not sure of the current cost.
PS: Have you budgeted for healthcare? SGK or similar?
PPS: Flights home twice a year to see family or attend weddings/funerals etc???