The extravagance that is forbidden on Eid
The extravagance that is forbidden is the one in which there’s excess beyond what is acceptable. That is, buying that exceeds what is necessary even though it is in a lawful thing. This is considered as an extravagance. It is different from the profligacy which occurs when buying unlawful things. Concerning wastefulness, Allah, the most high, says:
O children of Adam, take your adornment at every masjid, and eat and drink, but be not excessive. Indeed, He likes not those who commit excess. [Quran 7 : 31 ]
As the adage says: Anything that exceeds its limit has become its opposite.