The hourly wage for domestic helpers (incl. social security contributions) in Germany is between € 12 and € 18, with regional differences. The domestic helpers on Putzperle.de determine their hourly wage themselves based on their experience and qualifications - and they state this in their profile. Basically, however, the wage is a matter of negotiation between you and your domestic help.
You can find more information on wages here: How much does a domestic helper cost?