Some people make money off football. I think last year teams like Calgari etc. did decently for their owners. But their level of ambition is not compatible with the Arab investors. Their main motivation is, like others have said, gaining a new toy. After buying islands, planes and women, few things remain when you sit on a big pile of oil dosh.
Incidentally, A few top clubs do actually turn profits. What they share however are two things: 1. Roughly a century of consistent sporting success and 2. they aren't owned by a sugar daddy. Barca, Real, Arsenal, Bayern and United (the coming year, at least) all turn profits, due to insane revenue.
City's and PSG's long term budgeting indicates that they will turn profits as a hilarious attempt to placate Platini and his raised FFP finger. But those budgets border on fairy tales when it comes to revenue growth. I can't remember the exact figures but the revenue growth that City and PSG "expect" is absolutely insane. Real Madrid, for example, didn't get to a yearly commercial revenue of €170M overnight - that took decades and decades of winning.