Hun in NSW it's usual to go 1 or 2 days (930-330ish) when they are 3, then 2 or 3 days when they are 4 and going to school the next year. The preschools don't usually do half days - that happens in other states.

Have you looked into daycare or occasional care? They both work out significantly cheaper per day for us due to Ccb and ccr.
Some will specifically run a half day program for the *younger* 3yo's (ie those who have only recently turned 3 when they start or those not quite 3 yo - Feb/March bubs), in my area our preschool does that and I know of several other ones in the surrounding area that does it too, but then it also means that some kids who were Jan/Feb/March born were actually having 3 years at preschool, starting with a half day as a *just* 3yo, then a full day as a 4yo, then 2 days as a 5yo because they were going to be held back from school till they were 6. I think the preschool has cut right back on the early 3yos and they are not granted a place in preference to the older 3yo's (those already 3) so the half day has probably been phased out now anyway. I do not think that a 3yo needs 2 full days at preschool though, but that's just my opinion.