As a flyer'n'buyer in Australia, I've made maybe up to 8 purchases from the USA vendors like Apogee, Wildman, BAMA in the last 4 years. Shipping costs make you wince.
Tracking and insurance options are a must have in my opinion as I've had a couple not arrive. Shipping is a huge factor in deciding to press the "Buy now" button, and I couldn't count on both hands the number of on-line shopping carts I've abandoned in the last 12months once I got to the shipping cost calculator, or the discovery that the vendor doesn't ship internationally or that the vendor needs you to call them in-person to talk about a shipping estimate.