In Switzerland excessive speeding fines are based on income.

A French Mann doing 250 kmh in 2009 had to pay 70k.

A Sweede was also caught and the fine was estimated over a million but I don't know if it was ever paid.

https://www.blick.ch/schweiz/249-km-h-von-seat-bolzer-noch-l...

https://www.blick.ch/schweiz/bern/mit-290-km-h-auf-der-autob...

Not exactly an answer, but they risk losing the right to drive (not just in Germany - EUCARIS exists) and being forced to sell the vehicle Or Else, alongside whatever fines are permitted. For example: https://www.autoevolution.com/news/judge-orders-speeding-dri...

In Germany fines are fixed: https://www.bussgeldkatalog.org/german-driving-laws/. There’s a table on that page.

It’s pretty easy to get banned from driving.