I Googled "US Import duties" and snipped this after a bunch of looking around:
Postal Service, Couriers and Freight
There are three ways goods can be sent to you from abroad. In order to avoid costly problems, you and the seller of your goods should agree on which will be used the international postal service, a courier service, or freight carriers.
International Postal Service: Merchandise shipped through the international postal service is forwarded upon its arrival in the United States to one of U.S. Customs and Border Protection International Mail Branches for clearance. If the item is less than $2,000 in value and is not subject to a quota or is not a restricted or prohibited item, a CBP official will usually prepare the paperwork for importing it, assess the proper duty, and release it for delivery. This procedure is generally referred to as a mail entry.
Packages whose declared value is under $200 ($100 if being sent as a gift to someone other than the purchaser) will generally be cleared without any additional paperwork prepared by CBP. However, CBP always reserves the right to require a formal entry for any importation and generally exercises this option if there is something unusual about the importation, or if important documents such as an invoice or bill of sale do not accompany the item.
(Sorry, lost the link.) If one of us here buys an expensive SF like an L6 Porcy from someone offshore, I don't *think* it would be subject to duty as it was made here. The laws are complicated!
Larry