If you bring back goods worth more than $800 it has to be declared and a duty paid.

Judging from the changes (currently paused) to the de minimus shipping rules (also formerly $800) I’d expect the threshold to be lowered substantially. Possibly arbitrarily while I’m on a trip and have already bought the goods.

The risk being if detained by DHS for who knows how long is not worth saving $400 on a MacBook personally.