Not so. The maximum fine for serious GDPR infringements is up to 20 million Euros or 4% of global turnover, whichever is higher.

https://gdpr.eu/fines/ - 20 million euros or 4% of global turnover, whichever is higher. It's not capped; it's designed to be more harmful to smaller businesses†, but it does scale with business size.

† I mean, that's probably not the exact intention, but that is the effect of a huge monetary cap alongside the proportion of turnover. I also think 4% of turnover is problematic given the old Pinto equation (https://www.spokesman.com/blogs/autos/2008/oct/17/pinto-memo... ); I'd rather a cap set in the region of 150% of global gross profit, but capitalists would never go for that.

> […], whichever amount is higher.

https://gdpr.eu/fines/

No. You can be fined in the billions under the GDPR if your turnover warrants it.