I've travelled via FRA many times to India and back. Once via MUC.

Twice, I was advised to get a transit visa stamped in my passport by the consulate (my US visa expired and I had a paper approval or I was on advanced parole)

I have to say, both these times, I never passed through a border control or a visa check. so my visa's were not reviewed or stamped by anyone in Germany. It may have been checked/validated by the ticket agent at origin.

in the mid-1990's the cost was around 10 USD, now it is about 100USD. felt ripped off.