Seeing how the prices have dropped dramatically (to around a grand now from tens of thousands a couple of years back) it won't be long before they're awfully cheap...remember how expensive even basic black laser printers were when they came out?
Imagine being able to turn out little plastic bits and pieces...say interior parts...for your car?
The gun is an interesting thing...but it was an AR15 and he only made the grip and magazine parts of the rifle...the barrel and action were still steel or high grade alloys. They are what takes all the stress. A Glock pistol is sometimes mistakenly called a "plastic" pistol, but the barrel and action parts are still steel or alloy. The grip frame and other bits are polymer.
Here's a couple that just a quick Ebay search showed up...the rolls of polymer stuff to make whatever you want (even in glow-in-the-dark plastic!) are all there as well. Just search for "3d printer" and see what pops up...
http://www.ebay.com.au/itm/3d-printe...ht_2109wt_1270
http://www.ebay.com.au/itm/Fully-***...ht_2397wt_1270
They'll be a lot cheaper once China starts upping production as they get more popular!