Macka,
I think a couple of personalities have a lot to do with the prices in Sydney. One such individual sits at the auction and when the bird he likes comes up he just holds his ticket up until he reaches his price. This could be more than a monthly salary for some and he could purchase 4 or 5 birds in one auction. I saw one young bird he purchased at hills last year for $2700 get sold for approx $700 over a tme frame of less than 12 months later.
Also people sell birds at these auctions that are not surplus birds but good birds which they believe they will get more than their worth.
Quick cash.
to see the birds go to the Hills auction website, photos in the catalogue of the birds discussed.
http://budgerigar.com.au/hills/
Bye.