I find it difficult to find reliable numbers (since I work in a different industry), but it seems median entry salary for IT graduate is 40k€, which is 25k€ nett anually. I also find the middle-upper class difficult for germany (since salary upper class doesnt mean you are asset upperclass aka rich).
Personally I would say 25k€ nett is middle class; but here everybody wants to belong to the middle class so it usually has a wide stretch.
Big companies are unionized so salarys do not get that big, but are considered higher then in non-unionized companies.