This website do charge for delivery but quite a lot of products there are cheaper than iherb. Also some of the items are not available from iherb can be found there.
EDITED: please make sure the items you buy is not banned by Australian Customs. (no milk, no bee pollen…etc)
Vitacost has flat shipping up to 3.6lbs (1.63293kg).
If I recall correctly, there's a chart on the right side that will calculate the running total weight in the shopping basket.
There's also 3.2% cash back with Cash Rewards.