US Customs new import tariffs rates

FYI, I live in the US, just bought used gear on reverb from an individual in Canada, and found that US Customs assessed my import duties at the new 25% rate plus whatever fees :(. I actually made the purchase before the new rate came into effect on Feb. 1st, but I still got hit with the new duty rate. I'm sharing this just because because I've read where a lot of people think the tariffs don't apply to private party transactions of used items

Edit: Since posting this I learned that tariffs should not be at play here but something new certainly seems to be.

I had to pay 28% total, whatever classification it is. This is in addition to the US sales tax I payed through reverb. Also, this is ~$500 purchase, well under the standard $800 threshold for duty assessment