I can give a few guesses here as I’m a fiber person and familiar with wool.
First off, most of the wool comforters you’ve searched for that are more expensive, have probably been made in the USA- which makes the price higher. Second, Australian wool is very abundant and sells for a very competitive price versus wool grown in the USA. The wool isn’t washable, so it hasn’t undergone the “superwash” process, which adds to the price. Also, Bed Bath and Beyond labels this as “their own”- so you aren’t paying for a “Name”. Although I couldn’t find a “fill” amount or weight of this comforter, it looks thinner than many I’ve seen. The comforter says it is Imported. I doubt it is made in Australia, even though they use Australian wool, my best guess is it’s probably made it China.
I was looking at this particular comforter myself because it looks lighter weight than many I’ve seen.
Hope this helps.