moderation

As the foundation of true social life has been laid on moderation and maintenance of equilibrium, the holy religion of Islam has not ignored moderation and equilibrium in any circumstances and even in the matter of daily expenditure it praises those persons 'who are neither extravagant nor niggardly but keep the golden mean.'

Yes! Extravangance and lavishness are blameworthy in the eyes of Islam and are considered to be great defect in a man.

Imam al Sadiq (AS) says:
"Perfection lies in three things and one of them is regularity in life."

Imam al Baqir (AS) says:
"There is goodness for one who is not moderate in his life, because this thing (i.e not being moderate) is not beneficial for him either in this world or in the hereafter."

And the holy Qur'an says"
"Do not squander your substance wastefully, for the wasteful are Satan's brothers." Sura al-Furqan, verse 67