First world problems, but these are all cliffs where it makes sense to keep your income down. Losing 20% off the top line will reduce your income by closer to 10% if my math is correct.
We have a problem in the UK with higher earners dropping out of the workforce partly because of the tax incentives. I personally choose not to work as an employee in the UK because I would be paying more than 50% in tax.
Also if you're married, this amount is combined between spouses. And for some things like 3rd pillar unemployment funds, tuition fees and donations, we get paid 20% back regardless of our income previous year. Some years I got around 500-1000 euros as a tax return, but when I checked this month (for 2022), it was 0, as I didn't have any of these exceptions last year.
[0]: https://www.emta.ee/en/private-client/calculation-2022-basic...
https://www.veronmaksajat.fi/luvut/Laskelmat/Palkansaajan-ve... The lower tax bracket of 38kEur give a margin tax of a whopping 49,5% and it gets progressively worse after that.