You need to select prepaid tab and choose 365 days in order to get the phone for $251 shipped. This phone can be unlocked free of charge by using the link (tested and worked).
http://www.vodafone.com.au/unlock
To configure 3G access for optus sims. Use the link below.
http://optusau.wdsglobal.com/internet
Features
3.7" WVGA High Density display (252 PPI)
5.0 megapixels AF camera
Powerful 1.4GHz CPU (faster than Galaxy S and Iphone 4)
Android™2.3 (Gingerbread)
Might be upgradable to ICS later on (unconfirmed)
Specs
http://shop.vodafone.com.au/mobile-specs/buy-samsung-galaxy-…
Overall, the phone is good given the price.
It lags a bit after using it for a few days till I install Android Booster Free app and MT Auto Killer. It runs very fast now.
RRP $279 prepaid from Vodafone store.
its a good price for a descent phone