As a rule of thumb, I tend to be wary of volume measurements, but so long as you can figure out rough weight equivalents, it might not be terrible.
Question about the coconut oil: do you have any ethnic grocery stores in your area? Being in Australia, do you have any Afrikaans, or Indonesian/Thai grocers? Coconut oil is a BIG cooking oil in those cultures, and you can find generally find it there. When I lived in a more "ethnic area" of Denver, I used to get really cheap coconut oil at the Afrikaans market on Colfax. I would have to imagine that, given your geographic location, there is *something* there? Or do you have any specialty markets? Coconut oil is also big in vegan/allergen-free cooking, here in the states.
Shortening, as MareMare said, is a superior option (cost-wise... and I would honestly argue soap-wise, too
) to palm oil. It's generally really cheap, too, if you get the generic. I have to assume Aussie groceries have generics? Gosh I suddenly feel so clueless about Australia...
I do agree with MareMare in buying a fragrance in bulk. It might hurt your wallet initially, but in the long run it'll pay off. Lavender, vanilla, something citrusy or any floral you're particular to might be a good idea.
That's it MareMare: we're freakin' moving to Australia and opening an affordable soap supply store. Done! Million-dollar idea right there!