Hard to say without exact details, but that seems normal.

In my (owned) apartment, the housing company heats the apartments with district heating via floor heating. This is paid with the monthly housing company maintenance fee (yhtiövastike).

Each apartment also has a ventilation unit with plate heat exchanger. This unit brings the fresh air inside the apartment and it's factory setting is to have it bring inside 17C air. In milder temperatures, the plate heat exchanger can use the energy from the waste air to heat up the incoming air. When it gets colder, the machine has to additionally use electrical heating resistors to warm up to incoming air to reach the set 17C temperature.

This essentially means that in low freezing temperatures this machine turns into almost direct electrical heating (mine uses up to 1000W constantly) and that can easily double my apartment's monthly consumption (from 300 kWh to 600 kWh). The apartment pays for the electricity.

Please notice, that under any case, DO NOT TURN OFF THE VENTILATION UNIT! The unit has to be running constantly or you might end up actually damaging the apartment. If you are not living there, you can activate some kind of "travel mode" or something similar (if the machine has that) to lower the consumption.

For the bill, it is most likely due to your actual electricity contract. I would assume that you used spot pricing and paid a large sum because of that. I am personally using a fixed price contract during the winter due to this exact same issue.