I think the first step is going to be factories. There are such factories already. Shapeways, Materialise, Sculpteo, etc.. They cater mostly to artists or hobbyists. For example if you are a jewelry designer you can sell pretty much globally by uploading your design to these websites and let the manufacturing and shipping taken care of by these factories. All you need to worry about it marketing.

Then you will see the MrFixIt model where you walk down to corner store to get your parts printed.

The next step is probably power tool market. There's gonna be a machine in your garage performing such tasks.

And finally it might become a house hold appliance like your fridge or TV.

These machies are far from the ability to meet the kind of demands you describe. But given the amount of money pouring into R&D nowadays it is going to unfold in that direction over the next few years.

Right now its about paying 100 bucks for something you could get for $20 and get the ability of customization in exchange.