The costs were already studied in 2023 and were deemed cost ineffective[0]. The report contained three main strategies (VE1, VE2, VE3) with A & B plans for the first two. Costs would be in the range of 10-15+ billion with 15-20+ years allocated for construction time[1, p. 47].

[0]: https://valtioneuvosto.fi/en/-/1410829/report-shows-that-cha...

[1]: https://api.hankeikkuna.fi/asiakirjat/697c1f25-332b-40ed-9d6...