I snapped up a pair of unused inserts off gumtree for a couple of hundred and purchased my second pair from twosrus.com with a load of other stuff. Twosrus will set you back about $800for a full set of inserts (delivered), with their current discount.
I've not seen a strut replacement, other than Monroe, only inserts. Many picture the strut replacement, but I'm not sure that's what is sold (like on the ebay ad you've posted, as those pictured wont fit an AW11).
There are some cheap deals on Ebay from time to time but it all works out to be much the same as twosrus.com. My biggest gripe is with twosrus shipping price in general, I've asked if there is an alternative but due to failures in the past they're firm with the limited options. I've found a similar package from amazon would cost me literally half or less. Unfortunately they will not ship to Aus but they would be by far the cheapest.
The biggest advantage to twosrus is a whole heap of other parts you will struggle to find elsewhere and the piece of mind that what you're getting is 100% correct, when you're spending big bucks (lets face it, $800 for shocks is 1/5th the value of the car), you want to get it right.
Nick.