I think when the income gap is THAT big it’s generally fine that he pays for stuff. It’s not like it’s just a cheap train ticket he’s paying for he’s asking them to fly across the world regularly and most people can’t do this on a regular wage. I would hope he knows them so well that he knows they’d be there if he didn’t have any money as well.
Yeah I agree, this isn't a bad mindset. If you want people there, you make some effort to bridge the financial gap, and paying for their tickets/accommodation/experiences is fine if he's getting emotional support out of it. Now if he was bankrolling their entire life (paying for rent etc), that would be inappropriate and user behaviour.
I have a cousin who married uber-wealthy and lives in Andorra. She will sometimes randomly message me if I can get certain dates off and when I say I can, she'll send me a plane ticket and I know I won't be paying for anything when I go. I will of course take gifts or try to buy her a meal as a token gesture but I know she misses family and our home country (her husband is a different ethnicity and she's often alone there) and having me there does more for her than money. It can be a very beneficial mutual relationship as long as both parties remain appreciative.