Austrian food and drink price are generally quite reasonable by UK standards except close to tourist hotspots in places like Vienna, Salzburg and Innsbruck (oh dear!) especially those frequented by US/japanese. As you move away prices drop off. If you are staying in central Innsbruck you may have some shopping around to do but if you are in one of the surrounding villages things should be OK. If you are in central Innsbruck and things are desperate then try the mostly chicken chain "Wienerwald" at Maria Theresienstraße 12, not what you would call gourmet but they do keep a grip on reality when setting prices