Save

I see.

You can save 6 dollars.
You also can save yourself
the trouble of ~

I guess those two are different cases of appropriate usage of “to save”.


****

Yes, exactly!

"You can save 6 dollars" - Here, 'save' is used in the context of preserving or retaining money that you would otherwise have spent.

"You can save yourself the trouble of [doing something]" - In this case, 'save' is used to mean prevent oneself from having to undergo or deal with something troublesome or difficult.

These two sentences exemplify different uses of the word 'save', showing its versatility in English language usage. Both contexts are very common and correct ways to use the word 'save'.