When will it be israaf (wasteful) for a billionaire?

Answer

If a person spends on something which is not necessary for his normal use and comfort, then it will be israaf irrespective of him being a billionaire. Billionaire or middleclass or even lower class, the same rule applies. Spending unnecessarily, wastefully and for pride and show are haraam. One then becomes the brother of shaitaan. The Qur'aan Majeed exhorts spending the extra in the Path of Allah Ta'ala. Thus, the money a billionaire desires to waste in unnecessary mansions and unnecessary vehicles and the like will be great calamities for him in Qiyaamah.

If he indulges in excessive luxuries only because of the money he has, and not because he needs the items, it will be israaf.