It costs them a few pence per coin to make the fakes from cheap alloys in China. Perhaps a few pence more to import them in bulk. That still leaves them plenty of profit from a fake £2 coin. British £2 coins are one of the most valuable circulating coins in the world at the moment; that's certainly worth counterfeiting.
Remember, a fake doesn't have to fool everybody, all the time. It only needs to fool one person, once, and it's mission accomplished for the counterfeiters.
Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis