Generally fast shipping is about $30us from hk, snail mail is less. If you buy in bulk you'll save alot more even if you choose fast shipping. At my lhs it costs $24 for a set of foams, plus tax and it's over $50 for a set.
Much cheaper from hk.
Tip - Buy 30mm or 28mm rears and then cut them down to size, it makes a difference if you buy in serious bulk, otherwise it's not wirth it for a buck or two.