I think it is a waste of money eating in such a luxury restaurant.
我觉得在这么高级的餐厅吃饭是浪费钱。
I think it is a waste of time explaining this to him.
我认为向他解释这些纯粹是浪费时间。
I think it is a waste of time watching TV.
我觉得看电视纯粹是浪费时间。