I suspect its' not just the money - a lot of people in what the general public consider "exciting" jobs do it for the buzz - and there is definitely a buzz in working overseas in these sort of jobs. Generally they're a lot more dangerous than in the UK or USA etc but that just adds. They aren't boring, form filling desk jobs either.
You see a very similar thing in the oil business where people go off to work for Saudi Aramco - sure the money helps but it isn't everything - the challenges are greater, and you're not one of the crowd at home.