Duty Charges to US?

Curious what others in the US have had to pay in the way of duty charges/taxes on purchases from BrewPi. In general (not with respect to BrewPi) I’ve heard a few horror stories where people have been hit with a big bill from the shipper on international shipments and I’m just wondering what to expect on a $2-300 order?

I had a order about 2x that 4-600$ and the bill from FedEx was around 40-50$ i think