Didn't look at your numbers closely but I agree that prices for cellular internet are very, very high in Europe. I moved to Germany 2 years ago and I currently pay 37 euros or so for 2GB (horrendously slow, on Edge most of the time). Contrast this with when I go back home (Morocco). I pay 10 euros for 12 Gbs of extremely available access (and many hours of calls for few euros more). I rarely finish it even when on Apple Music for hours a day.
I honestly do not know which plans you refer to. Remember that I mentioned 10GB is worth 10 euros in some other countries (actually less, since I pay 100 Moroccan dirhams, which is less than 10 euros, and yes, it is blazingly fast, I stream Football matches through it). Can you think of any plans even remotely comparable in Germany? I'd switch in a second if there is one; I do not pay for my device and my contract is month-by-month.