Germans are not willing to pay money for food. They expect food to be cheap, they don't care too much about the quality of it (in general, of course).
Germans sometimes joke about themselves that some of them will spend +1000€ for a barbecue without a problem, yet they'll put the cheapest 0.50€ sausages on it.
I could not disagree more. I actually never met a german who joked about being cheap with food. Quite the opposite is true.
Also the per capita household expenditure on food[1] is above the average of European countries. Higher for example than in the UK or Austria, which have comparable incomes.
I live in Berlin and used to live in Vienna - I hear such jokes all the time, that Berliners will eat just about anything as long as it's cheap and won't immediately kill you.
You don't have to go far to see the difference either: Austrians and south Germans are already much more "food-oriented" than north Germans, so this may be a regional thing rather than encompassing the whole country.
The joke isn't by Germans saying they eat cheap food but by other immigrants saying it about Berliners/Germans (i lived for a much longer in Austria and never heard this said about Austrians).
I think the locals wouldn't joke about themselves that way cause to them the way they are is just "normal".
And surely you've heard Berliners say that Berlin's local food tradition is the Döner (i.e. there is no "local food")? I guarantee you no Bavarian or Austrian would say that about their own food tradition.
(And BTW I have no ill will towards Berlin or Berliners, I think it's one of the best places in the world to live in)
