I pay the slightly above average Telekom price because i appreciate the stability of their service and their very good tech support.
Telekom's tech support in the city I used to live in sucked huge donkey balls. It was fucking awful. Everything took ages and communication sucked. I was once without internet for 3 weeks and I called them all the time, complained at the local "T-Punkt" and so on.
They've outsourced lots of tech support and you can get really unlucky if you live in the wrong city.
I'm now with Kabel Deutschland which offers a 100mbit connection and have 0 issues so far.
So yeah, mileages vary.