Yeah, a lot of freshwater fish are banned imports. You can import them with some special permit and a mammoth load of paper work and stuff from the government and DPI&F and AQUIS. But it costs too much money.
The reason they are expensive over here is because they smuggle them into the country. It's very risky business, so people charge high prices. But $1500 is an odd price. The lowest i've seen is 2k a pair, that was for motoros.
Saltwater fish can be imported fairly easily, the only things you need are an import license, and a quarintine room which AQUIS will come and check every two weeks.
It's easier to ask an LFS to get them in for you. One of the best online stores for saltwater fish in Australia is
Keysborough Aquarium. they ship australia wide, and from my understanding can import themselves.