Hyphens are almost always aesthetic. They aren't really necessary, they just help the reader understand that the the hyphenated words are tied together.
the marginal benefit of that action exceeds the marginal cost of that action.
It is not hyphenated.
Motorcycle is not hyphenated
No it's not hyphenated.
words are only hyphenated when they have a separate meaning when separated than they do when hyphenated
Yes it should be hyphenated.
No, "hardworking" is not hyphenated.
It can be. Some words can be seen both hyphenated and non-hyphenated.
No. Well above is not hyphenated.
peace of mind is not hyphenated.
No, "homework" shouldn't be hyphenated.
Yes it should be hyphenated.