No, it's only expensive compared to every other generation source that is not expected to price in externalities. When I get to vent my waste product into the open air my mwh is way cheaper!! Who could have guessed? How much does a natural gas plant that captures all waste output cost?
decomission cost and waste management costs are included and cheap. You should avoid informing yourself from some politically motivated websites and rely on real financial data like https://www.kkg.ch/de/uns/geschaefts-nachhaltigkeitsberichte... or check the Onkalo project