I would say your best bet now is to regularly check ebay and the amazon marketplace and wait for a decent price to appear.
If you're in the US, the cheapest I've recently seen it for is on the amazon.com marketplace at $90.
If you're in Europe you can purchase it for €99.50 from www.cheap-comics.com
I wasn't going to pick this Omnibus up at all, but I took Krisis's advice and purchased it when it was going at clearance as an "investment".