I don't think so. The development is in City of Canning and the troy bz is asking thewesternfront how they are getting on with the City of Canning engineering department. I have a mate doing a subby in Canning ATM and they are finding the Council a PITA.
Going from recent sales in the area I think those prices are under (depending on the land size component of course).
For the 3x2, recent sales examples:
$585,000 (http://www.realestate.com.au/property-villa-wa-st+james-117999095)
$589,000...
In Perth I can get a two storey townhouse built for $300k turn key. Single storey sould be less but I was thinking 420k might be a bit on the low side depending on the size and on whether that price is turn key of course.
Looks like a good project though. I think St James is a great area!