It’s still not earning you money to spend electricity because you still have to pay the transfer fee which is around 6 cents / kWh but it’s pretty damn cheap nevertheless, mostly because of the excess in wind energy.
Last winter because of a mistake it dropped down to negative 50 cents / kWh for few hours, averaging negative 20 cents for the entire day. People were literally earning money by spending electricity. Some were running electric heaters outside in the middle of the winter.
No, it does have a reality. The problem is that an electricity grid can collapse, due to too much electricity. However some power plants can not be easily shut down. Nuclear for example can be throttled to about 50%, but shutting it down requires a restart, which takes a day. So loosing a little money for a few hours can be cheaper then a full shut down. There are other effects, like district heating power plants, which are needed to provide heat, hydro power, which has too much water in the reservoir and waste power plants, which have to burn the waste at some point.
Then you got to keep in mind that Finland is fairly is a country with a small population, which is rather isolated. They cut the power lines to Russia and Sweden and the Baltic countries are also low population and especially Sweden also has a lot of low carbon electricity. So export is not an easy option.