Ok social insurance taxes are quite high here, too. Income tax is definitively lower for 24,000 Euro income per year. (And actually I don't consider 2000 Euro per month as pretty crappy. A net income of ~16kEuro per year is close to the median income in Germany, and considerably more than phd students typical income.)
However, e.g. the retirement social insurance afterwards pays out according to what was paid in before. So there is some reason to keep in place some of those contributions.

Der Amerikaner ist die Orchidee unter den Menschen
Volker Pispers