I don't think you can compare people moving abroad to people moving to the UK, it's a totally different ballgame.
There are two types of people who move here.
1) To try and live off the state
2) To try and make a living through hard work
And Brits moving away
1) To buy somewhere in the sun, and relax in a nice place! (with their own money)
2) To move away and work in that specific country.
Back a few years ago, it was possible for anyone to move here and take advantage of the country, make a lot of money and become extremely rich in a short space of time if you had the brains to do so. House prices were pretty cheap, and the rich could buy the biggest houses without the banks help in London for a days work. It's not the same anymore, the market is more saturated, and people don't wave their cash around like they used too.
You do get a fair few self made millionaires every year, but it's not in the same league as before
imo.