I ordered a jacket from scottishkilts.net and paid about $35 in duty (paid on delivery). My kilt from them cost me around $40 in duty (billed later). Now both of these came via UPS, a company that acts as their own broker and can add their fee to the duties. The sealskin sporran I ordered from scottishkilts.net came via post (Parcel Force ) and took a few more days to arrive, but I paid $0 in duties or taxes.

There are tricks that some companies can do (listing the wholesale price rather than retail, or using a courier that doesn't broker themselves). Just be wary of Fed EX, DHL, and even UPS to some extend. Yes, they are reliable, but you'll pay way more.