As a person who has received invoices for hundreds of thousands of dollars worth of miners Customs Duties have always been $0, unless the tariff code was entered wrong, however there have always been Customs Fee's and Brokerage fees, either with private brokers or UPS/Shipping company brokerages.
Ok call it Customs
fees and brokerage fees, either way it's has been very rare I've had to pay them and since I've gotten at least 1 or 2 of pretty much all of Bitmains generations of batch-1 miners - they've been pricey.