Forgot to add the 55 € for 16 GB of RAM to the expenditures. With the Unity project getting bigger and bigger, I was regularly filling up 16 GB. Just opening one larger Blender file in addition and that's it. Now with 32 GB in total it should be good for a while. At some point I have to upgrade the whole PC as it's almost four years old already.
It's funny how people complain that four year old hardware is a steep requirement for a new game (RTX 2060 for KSP 2). Twenty years ago you had to upgrade every two years to keep up with the hardware requirements. Granted, GPU prices are just coming down now after the Ethereum and Covid hell. I guess, I was also a little lucky getting my GPU right before it.