There are different prices in different areas. My idea of a good deal is two decent main courses and a couple of drinks for less than £10 in a comfortable restaurant. The normal price of a main course round here (Yorkshire) is £5 - £8, depending where you go, what you eat and so on. Promotions might do two main courses for £5.95.
Yesterday I bought 5 instant microwave meals for £4 at Asda. I reckon that they would just about pass for a restaurant meal - or maybe the 2 for £2.50 ones would give a better sized helping. All I need now is a few Asian posters, subdued lighting and the right music and, if people think £5 a go is a bargain, I'll start hiring the staff...
A few years ago I picked up the bill for feeding 8 people in a plush restaurant (carpet on the walls, marble in the bathroom, etc) in the financial district of Manila. It came to £13. A friend took my receipt so it could be claimed as a business expense.