Hi Alfred,
to the site!
There are a few bino retailers in the Sydney area, including Bintel, Andrews Communications, MyAstroShop and Astro-optical.
There's a review of the
Fujinon 8x42 in the Reviews section, and I think John B (ausastronomer) has some experience with the Pentax.
All 4 you've listed are in the more expensive range, and will be better than no-name or Saxon type brands, so you're off to a good start.
When looking at US prices, you have to factor in postage costs, which on a pair of binos, might be significant (US $20+).
Obviously buying local gives you local support - they also have to pay staff, rent etc so it's bound to be more expensive than buying online.