Actually the price of electricity in Finland is among the lowest in Europe. This is one of the chief reasons how our system works. You see, we have a lot of traditionally extremely energy-intensive industry related to forestry (i.e. paper, carton and cellulose production), metalworks (both smelting and advanced machining such as shipbuilding) and so on. As a result, one of the primary goals of the entire country's energy policy is to ensure that electricity would be as cheap as possible.
This kind of forward planning is what allows for those record profits. Not electricity prices, that are very cheap in Finland by European standards to the point that it was one of the chief reasons why most of the heavy industry stays in the country, and why modern energy intensive industries like heavy datacenters (i.e. Google) find Finland so interesting for their European operations.
Some other things you should understand before arguing on the topic of "eating profits".
1. Loviisa site is owned by a different power company, Fortum. Olkiluoto is owned by TVO. The third planned nuclear plant site is by a third company, Fennovoima at Pyhäjoki.
2. Financing in modern world is done through credit rather than through running profits.
3. Areva has actually agreed to fixed price delivery. Which is why Areva has done huge write downs for the plant. Most of the losses related to Olkiluoto 3 that TVO, the company that runs Olkiluoto site come from having no ability to produce power as planned and having to source energy elsewhere. Luckily we have solid interconnects with Russia (mainly Sosnovy Bor nuclear plant), Estonia (Narva's shale rock plant) and Sweden (Hydro across northern Sweden) to pick up the slack when needed.
4. Nuclear industry is considered so profitable here in Finland that third site by a separate company is in advanced planned stages. Fennovoima has selected a Rosatom reactor for a Pyhäjoki site just recently. To give you an understanding of how far decision making is on this, our government had anti-nuclear Green party as one of the smaller parties within it, and it ended up resigning from government when other parties, including much of opposition parties voted to proceed with the granting of necessary permits.