If they're offshoring the money and/or living off rent instead of building productive businesses and investing in the future, their net contribution is negative.
So you're saying its worth it to keep these guys because while they do cheat the system to not pay MILLIONS in taxes. Through VAT they do pay a few pense in taxes. So its ok?
I'm not sure that's quite the argument you think it is? The fact is that losing a thousand well-off selfish people is not really going to put a dent in the UK's financial well-being at all is it? This is not a question of 'for the better good' at all. There are hundreds of thousands of very rich people who choose to stay and contribute to the society in which they live. Which is admirable.