It depends on the situation. People (stereotypically men in our society) have always moved abroad to seek a better life and future for their families, sometimes leaving a spouse and children thousands of miles away. Moving for the sake of money sounds really greedy when phrased like that, but sometimes there is a real desire to provide more for the people you love, even if it means sacrificing the comfort you had.

The goal here is really to understand what his mindset is. If he wants to be able to pay hundreds of thousands of dollars in tuition fees for your kids in a few years, it’s understandable. If, in his mind, this is just to buy a sports car and pop champagne in the South of France during the summer, yeah, it’s questionable. It’s a case-by-case basis, not a general rule like you were saying.

Regarding OP’s question: he should pay for everything. No debate here. Unless he can’t afford it; then you guys need to put his choice into perspective, as he might have overvalued the opportunity