“There's no point in buying a costume if you're not even going to wear it out.”
You and your husband don't have any plans to do anything for Halloween. You were just going to stay home. But your husband sees a costume that he wants to buy while you're out shopping together. You don't think he should buy it because it's a waste of money, so you say this.
There's no point in buying a costume if you're not even going to wear it out.
There are two meanings of "there's no point in ___ing":
If you try to do something, it's not going to work.
There's no point in cramming the day before the test. If I don't know it by now, an extra day of studying isn't going to help.
If you try doing something, it will work but there won't be any benefit from it. That might be because you already have what you need, or because you'll get the same effects whether you do something or not.
There's no point in studying for Professor Clint's exam. His tests are always so easy.
The first definition of "there's no point ___ing" can also be expressed with "It's no use ___ing." The second definition can't:
It's no use cramming the day before the test.
The phrase "wear ___ out" has two meanings. One meaning is to use something until it's worn out:
I love this jacket. I'll keep wearing it until I wear it out.
But the meaning of "wear ___ out" that's used in the example above means to wear something to go out somewhere. In the situation at the top, wearing the costume out means going to a party or parade.
Notice that for the first meaning of "wear ___ out", you can also say "wear out ___":
It takes a long time to wear out a nice pair of shoes like those.
But you can't say "wear out ___" when you mean "wear something to go out".