I thought most postdocs in Germany were on TV-L 13? That should be at least around 2500€ net, right? If you're at 100%, of course, but I would think most postdocs are.
Yes, you are right. Academia is subject to a wag agreement and 100% E-13 corresponds to roughly 4000€ gross (brutto) and 2370€ net. Cf. http://oeffentlicher-dienst.info/tv-l/allg/