Is it permissible to spend 800 pounds on the wedding day for an outing, a gold gift, and flowers for the wife, or is that considered extravagance?

There is no harm in a husband spending on his wife for permissible matters, as long as it does not deplete his wealth. He is hoped to be rewarded if he intends to bring joy to her and honor her. However, if the amount is large and detrimental to his wealth, then it is considered extravagance.