And spot market prices last December when all six plants were running at full power were as high as they are now. This has nothing to do with nuclear energy. It's demand pushing Germany to run more expensive power plants, which in turn dictate the price of electricity for all power plants, so pointing at the electricity mix of Germany is a waste of time.
"Nuclear power in Germany accounted for 13.3% of German electricity supply in 2021, generated by six power plants, of which three were switched off at the end of 2021, the other three due to cease operation at the end of 2022 according to the complete nuclear phase-out plan of 2011." https://en.wikipedia.org/wiki/Nuclear_power_in_Germany