PSX & PS2 ? buy a ps2 for like $50 if you want to play the old titles.. Bluray? by the time region encoding truly kicks in, standalone bluray players with more features will be probably around $300-400 mark.
These days, really, by the time you factor in $50 shipping, console for around $700AUD and a transformer you won't save much though so it doesn't make sense to only save $100 you're right. Few June specials around now on PS3 as well here in Oz.
Ebay has always been a rip.. I love it for selling, buy very little.
If you want to buy games online, gameswarehouse.com.au, gamehead.com.au, and jbhifi.com.au all have pretty good prices. If you buy 2-3 at a time you'll discount the shipping cost and may work out a bit cheaper than most stores.
It's hard with the retail environment at the moment - the games are very much fixed by the publisher, and to some extent the hardware manufacturers.
If a few retailers have a whinge about any other retailer trying to sell games too much lower than the RRP, therefore cutting into their profits, they'll quickly let the top of the chain know that they may consider not selling titles from that publisher, or entire console altogether. Obviously then pressure can be exerted from the top on that retailer to ensure that prices don't go too low.
Rumour has it the reason the PS3 is $999 here, and not $720 ish as per japan and the US, is that Harvey Norman and some of the larger retailers demanded that Sony gave them a RRP price, that allowed a $200 or so profit on each console. Their old model used to be 'as long as we make it up on the games its ok', but I guess they got sick of that... and soon as people pirate too many games they lose out on sales as well.