If you were a super famous GM, like Anand and Carlsen, that would be no problem, because there are sponsors.
As an amateur, however, it can indeed became expensive.
Professional players that have not yet achieved the high class level suffer way more, I believe, because they are often without sponsors and need to gain enough money from tournaments to compensate the expenses and fees and also make a living.
How were Anand and Carlsen able to play in these type of elementary tournaments? I don't mean them specifically, but how did these GMs manage to get into elementary tournaments and start their career.
I presume most GMs did the way I said, taking part on tournaments without knowing if they will end with more or less money than they started.
But if they get a high status early, before adulthood, they can pass trough this fase while still under their parents financial support.
What about chess in London? I am going to study there. If you know any chess clubs, let me know.
When I visited London as a tourist, I joined http://www.khcc.org.uk/start.shtml my first night in the city. Played a few games with Kingscrusher of YouTube fame.