Feel free to not declare international purchase at your own peril. CBP doesn’t search every bag. Sometimes if your declaration is close enough to the limit they don’t care. However if they do search and you haven’t declared, you’re going to have a longer border crossing than normal and very likely that will be the case in the future.

There are tariffs on many or most things under this administration. No matter the form of import (mail, carried personally, courier), you will need to pay the tariff.