"Far" lower wages? Progressive income tax is constant at 42% for essentially the whole salary range that is relevant for an engineer (66-278k).
As a concrete example, total tax burden at:
- 70k is ~40% (42k net)
- 100k with ~44% (56k net)
- 200k with ~46% (107k net)
I'd seriously question the judgement of any engineer that chooses e.g. the part time job that gives you 42k net over the full time job that gives you 56k net (= significant difference of possible living conditions/disposable income) _purely_ on the basis that you earn "far" less per additional Euro. (I think it would be very understandable to choose the less work hours just for having more free time to spend on other things.)
I feel like there is almost an inverse effect once you hit the limit on social contributions (~90k), where it becomes more motivating to earn more, as from that point "only" your income tax increases and health insurance etc. stays steady.