I've looked into it and 'a good wood lathe' is not cheap (relative to say an inkjet or a laser printer) and neither is a 3-D printer. If you need to be able to print any size of item, your printer has to be capable and that starts to cost money. And the materials must be a bit pricey.
Shapeways (look em up on Google) does vast amounts of this stuff and a lot of starship miniature manufacturers are using something like Google Sketchup to draw a three D file and ship it to Shapeways to either make their product directly (just adding a markup) or else to make a mould master which they mould and cast in resin. But if you go to buy such ships commercially from Shapeways or from games companies, you will find them very light (possibly easier to destroy than resins or white metal) and at least as expensive as the other two options. At least that has been my experience as I build an extensive Stargate Universe fleet from various manufacturers.
I looked into what the cost of making a 25-28mm APC or tank would be and they won't be cheap. Of course, resin generally has gotten very expensive so that might just be an overall trend. But if you make your own master, cast it in RTV, and then crank them out with bulk resin purchases, it is a fair bit cheaper (like at least half the cost) or ordering an equivalent off a 3D printer.
It does put stuff in reach that never was and for small parts or ships, it is great. But for bigger stuff, especially stuff that might have been done with a hefty chunk of material, it is quite pricey.
o: I had never seen that before and was fascinated. It sounded very slow, tedious and time-consuming, but I sense a new wave of consumer goods manufacture in the offing.
