I wonder if we'll ever see on-demand assembly of stuff like this. That is and has been done. Like for the Moto X, which is custom assembled if you do a custom

I wonder if we'll ever see on-demand assembly of stuff like this. That is and has been done. Like for the Moto X, which is custom assembled if you do a custom order. However, there is a substantial ongoing cost to keep a manufacturing line up and running for a product. If you're not currently running phones (or whatever product) every day, then you'd want to use the line space for other products. This implies setup / teardown costs and (re)training. In general, the manufacturer would prefer to start running the product at some given volume per day, be given plenty of notice to scale up or down the volume, and then cease production and be done with it. That minimizes their costs.