Is a husband's purchase of a new car for 100,000 after four years of buying a car for the same price considered extravagance for which he will be held accountable? And is it permissible for the wife to supplicate against him because of this? And will her prayers and supplications be accepted with her action? And what is the punishment for that?

A wife is not permitted to discipline her husband for his sins; rather, she should advise him and forbid him from evil in a kind manner. It cannot be definitively stated that what the husband did constitutes extravagance, as the definition of extravagance varies according to a person's circumstances. It is not permissible for a wife to supplicate against her husband unless he has wronged her, and only to the extent of his wrongdoing without transgression, though forgiveness is better. Her supplication against him will be answered, Allah willing, if he has wronged her and she has not transgressed in her supplication. Transgressing in supplication does not affect the acceptance of her prayers, and her punishment in the Hereafter is for Allah to decide.