As 237SJ suggests, it might depend where you live.
For example, someone who shops at Norwich Market expects to pay just £3.20 for a superb 'hog roast' roll, packed with as much succulent slow-cooked pork as it's possible to fit into a large bap, with beautiful stuffing, apple sauce and crackling. A coffee from a neighbouring stall costs 60p. (Those are the prices I paid a fortnight ago).
So someone who uses Norwich market would think that £3.00 for a basic burger, sourced from Asda's freezer section, was grossly overpriced. Similarly, they'd baulk at paying £1.50 for a coffee.
However someone who shops in an upmarket town in the Home Counties might have to pay £6.00 a the hog roast bap from their local market, and £2.30 for a coffee. So they'd probably see £3 for a burger, and £1.50 for a coffee, at a church fete, as quite reasonable prices.