Some parts are imported but it‘s probably as European as possible at the moment. Details about production can be found here: https://www.nager-it.de/en/maus/fertigung. Unfortunately their shop seem to be only accessible in German.
credit: https://www.reddit.com/r/BuyFromEU/comments/1ngg5r6/fair_and_european_computer_mouse/
You need to add more slavery and exploitation to the production method to make it cheaper.
I don’t have a problem with the price. I spent 70€ on my mouse, but I will not use a mouse with no side buttons in 2025…
Or just mass production…
Economies of scale play a role too, and China certainly has that. Neglecting the environment and employee rights aren’t really a big deal in there, but in Germany they are. On top of that, there are also big differences in living standards, which is reflected in the wages. All of that stacked together, and you end up with massive price differences.