Fair point. My personal definition of a reasonable living standard, is being able to save a house deposit and eventually buy a 2-up 2-down terraced house, without forgoing all social life or basic no frills holidays. Such as house costs £70-80k in a cheap part of a northern city, £120k in a more up-market part, and, as for London, well maybe its under £300k on the very last stop on a tube line - Morden for example.
In London you're likely to end up in a shared apartment for years. It might be a nice apartment, with good housemates, but it'll never be yours, and what happens when you get married and have kids? Lots of people answer "well then I move a 45 min train ride away". My other definition of decent standard of living involves not paying out thousands of £ to catch a stressful crowded train every day. ;)
That all depends on your definition of "great standard of living". I started out on £20k and have never felt that I was slumming it in London.