What is the cost of driving the Audi (B8) 3.0 TDI?

Hello! There are quite nice computers on the internet that calculate what the km drive costs by car. The problem is that they throw everything into the balance like insurance, taxes, etc. But that doesn’t quite fit, because the car is registered anyway and taxes I pay also, whether I don’t drive with it for a while or not. I’m interested therefore, how I can calculate what the km drive costs me without these o. g. factors. needs to calculate for the distance and the wear. That’s almost it, isn’t it? The loss of value may be even more pro rata, because it also loses value, if not driven with it. Does anyone have an idea how to calculate it reasonably?