Updated description after people provided before prices - thanks.
Some great bargains at Living Edge on Herman Miller chairs. These do not come on sale very often and are the cheapest I have seen for these models (there are different variations on each chair - the below ones have essentially all optional extras). Yes, they are still expensive. They do have 12 year warranties and are IMO worth it if you spend all day at a computer screen.
Shipping is $60 in Sydney or free pickup in Alexandria warehouse.
Here are some examples:
Aeron Size B($1250)
Not many stores in Australia sell these. The compare prices above are pulled from badbacks.com.au because I couldn't find the 'before' price on LivingEdge - e.g. for the Aeron.