2012 Pepperjack Shiraz only $16.99 from Jims Cellars in Sydney - Easter Special. This is normally $21.85 in any six at Dan Murphys, $28.99 on Crackawines and $22.80 at 1st Choice. Kemenys also doing special at $16.99. Great Drop - 93 points and winner of the 2013 Visy Great Australian Shiraz Challenge. Jims delivery to Sydney is $5 per carton. Don't know about other states / regional areas.
It was less than this at Dan Murphy recently - but I'll give you that this is probably the cheapest at the moment.