Whether they feel trapped I'm not sure but a girl I used to date worked in the city and she was definitely trapped.
She worked for a large bank in the finance sector and felt she had to play keep up with her colleagues and more importantly her managers on the social scene. This meant that she would often go out to dinner/drinks a couple of times a week. Obviously you need to dress smartly to work in the city, so had a clothes bill too. Lunches, make up, hair dos, nails, yoga and so on. It all adds up
She was probably earning somewhere in the region of £50k, which isn't bad I guess, but used credit cards and loans to keep up appearances.
I felt that she was locked in, with no choice but to continue working in London to earn the money to pay the bills she couldn't afford.