Even taking into account all OL3 construction delays the long term LCOE target for all three plants is 30 EUR/MWh. LCOE for the OL3 reactor alone is estimated at 42 EUR/MWh.
My "envelope maths" tells me that generating electricity from OL3 is twice the cost of OL1+OL2: 18 EUR/MWh vs 42 EUR/MWh.The main Wiki article includes a long list of reasons for delays and cost overruns.
The construction project also included very long term, underground storage. On YouTube, you can find a great, if slightly creepy, documentary about it called "Into Eternity".