Not really. A board for the book spine would have been like 4 square inches. You can get three copies of a board for $5 per square inch from OSHpark so $20 total. I doubt 3d printing something of that size is any cheaper.
I think you misunderstand 3d printing costs and time. $20 gets you an entire kilo of standard plastic for printing. I highly doubt his enclosure setup took more than 50 grams to print, or about $1 total. Total printing time was likely under 5 hours.
PCBs are over an order of magnitude more expensive and generally have a two week lead time unless you fab them yourself on a cnc or laser setup. Also, what do you do if you realize you messed up something in your PCB setup? You have to wait for a whole new batch or else toss it and wire manually anyway. With 3D printing, you just modify the model and print a new version in a couple hours.
For one-off prototypes like this a custom PCB is a really iffy proposition.
Only if you already invested several grand in a 3D printer. A service like shapeways is similar cost and time to getting a pcb made. A pcb milling game machine is the same cost as a 3D printer.
You're again overestimating costs. A perfectly capable 3D printer can easily be had for under $500 and serves many more purposes than just fabbing PCBs. Many, many places (including libraries now) have 3D printers available for use at low cost. A mini mill capable of milling a PCB is harder to come by and also not useful for much more than basic engraving.
