Those prices you quoted, WM, are more or less the prices you'd pay at a non-league football ground. At a league match, expect to pay at least £1-£2 per item on top of that. What I really resent is £1.50 for a polystyrene cup of tea which is nothing other than a tea-bag in hot water; add your own milk.
We have a large street food festival in central Birmingham, I think it's biennial ... numerous stalls offering Caribbean, French, Spanish, German, Polish, so on. You'd be paying a minimum of £4-£5 per (not very large) portion, and you are right, it's a complete rip-off. The last time we went, we wandered round, had an Italian ice-cream or similar each, bought a pork-pie from the English Farmers stall for tea, and went home.
It's a bit like Birmingham's "Frankfurt German Market" every December, and that's another mega rip-off.

The award-winning stollen's about three times the price of Lidl's award-winning stollen (have you noticed how everything's won an award - who grants them, I'd like to know .....

)