I was concerned about the shipping prices as well (particularly since it's such a small item but shipping is $9.30) but I was surprised when I actually had a sale from the United States. So it really depends on how much a buyer is willing to pay for the item.
In regards to where I sell, I've just recently started out on Etsy, but my first sale was on eBay. However, I don't rely on Etsy to bring the customers 'through the door'. Before I even started selling, I made sure to build up my name on deviantArt so when I did start selling, I already people following my work..though that doesn't guarantee sales ^^; so other advertising will be a must also.
With combined shipping, the way I work it out is to estimate how much additional weight each item will be and work it out from there. So for example, 1 item will cost $9.30 (up to 250g) then my next item will be an additional $6.00 because the next weight up (up to 500g) Australia Post charges is $15.30. Of course I also add a small fee on top of that for packaging materials.
I hope that helps
Good luck on your venture!