A full meal including drinks will usually run 50 chf per person if you’re a couple most meals will run 100+ - it is possible to eat on a budget (we’ve usually relied on sausage stands and donair). And yea, I’m mostly talking about what you’ll find in Lucerne, Zurich, or Geneva where you’re likely to visit.
Stay overnight next time! The town surrounding the citadel is actually really pleasant and one of the staples of cuisine local to that area is Cassoulet!