Its the fact that we are mandated to sell the excess to EU before we take care of our own.
That doesn’t really work that way and there is no forcing involved. Capacity is sold by the power plant operators and bought by the power companies who resell it then. As long as neighbouring zones pay more than Southern Sweden, power plant operators in Southern Sweden will sell their generation capacity at that higher price because they are not a charity but for profit companies.
Now, grid operators in Southern Sweden could show them the middle finger and buy capacity from Central Sweden, but that’s apparently not possible because not enough power lines exist to actually transfer the energy from there. So, grid operators in the South are stuck with the higher prices that someone else pays as well.
And even if you just want to blame the Germans for everything, check the distribution of exports from the South Sweden zone before making that claim: https://app.electricitymaps.com/
When you entered the scene before epoch 0 I guess it is.