Target on Ebay have 20% off until 21st February, using discount code "CTARGET" at checkout.
It looks to apply to everything on Ebay by Target (Australia), but the email I got from them promoted toys... and unfortunately, the only Transformers toy I could find on their page was Devastator at $300, which only brings it down to $240 with the discount (which is still $42 more expensive than BigW).