Posting overseas is SO expensive

Tonight is the 5th time I've been asked if I'll post an item to an overseas buyers (I don't have this option selected). I have my Aus Post booklet and check the website for exact location costs, but the 2 times I sent overseas, I was left a bit out of pocket because I misunderstood the Aus Post information. I didn't bother the buyer with it as it was my fault. One was to the USA and one was to Sweden.

So this newest buyer is from Brazil, and the cheapest prepaid satchel is $28. Um...the item itself is only $12.

I just feel like I'm appearing like a bad seller as I basically have to tell these people that yes, I can send it but...the cost...