It was narrated that Anas (radi Allahu anhu) said: "The Messenger of Allah passed by a dome-shaped structure at the door of a man among the Ansar and said, 'What is this?' They said, 'A dome that was built by so and so.' The Messenger of Allah (sal Allahu alaihi wa sallam) said: 'All wealth that is like this (extravagant) will bring evil consequences to its owner on the Day of Resurrection.' News of that reached the Ansari, so he demolished it. Then the Prophet (sal Allahu alaihi wa sallam) passed by (that place) later on and did not see it. He asked about it and was told that its owner had demolished it because of what he had heard from him. He said, 'May Allah have mercy on him, may Allah have mercy on him.'" [Ibn Majah - graded hasan]
The motivation behind extravagance is usually to receive others’ praise. Once a man passed by a fine building and praised it. The pious man accompanying him remarked: “It is these words of praise of yours that compelled the owner to throw his money on its construction like this (and he swept his hands out with a flourish!)
Each person is best at taking account of his/her own life and what is extravagant in it.