IKEA Marsden Park NSW and Logan VIC will have a Labour Day long weekend sale for IKEA KIVIK Three-Seater with Hillared Anthracite cover, link here.
Normal price is $699, which consist of $390 base sofa without cover + $309 Hillared Anthacite cover. IKEA almost never discount their base sofa (unless it's discontinued), so basically you're buying the cover for only $9. For reference, the cheapest cover available for three seater KIVIK is Orrsta light grey for $109.
It's not very clear from their offer page but usually they still separate the base and cover, so if you already have the sofa you might be able to get just the cover for $9.
Awesome, looks like this offer is at the Logan store too.
http://www.ikea.com/au/en/store/logan/offers_activities (Scroll to the bottom).