The Deck!

Surfer Boy came home last night and asked me what we were having for the deck. The DECK!!! Holy crap I haven't thought that far ahead - I assumed we'd do this a some distant point down the track.  Apparently not!!  (Lots of exclamation points in this post to show my total surprise)  Turns out we really need to do it ASAP as the house is so high off the ground at the back that it has to be done or the house won't get signed off.  We could add temporary steps but that seems a bit of a waste so now I am feverishly trying to decide on deck timber.   

The deck will be a large square pretty much, and wouldn't you know it - every picture I pointed out to SB proved to be astronomically expensive.  At this end of the build we are trying to be as careful as possible with money and of course the timbers I keep showing him are far from the cheap end. 
Ideally I'd love large, recycled timbers that are untreated.  According to SB there are 2 problems with this - price for recycled timber and maintenance as untreated timber apparently will warp and rot out eventually.  Bugger bugger bugger. 

There has to be something out there that will look like this (below - my perfect deck) - but be cheap and resilient! Any ideas???