Flicking between two TV channels (a thought experiment)
On one channel is a 'How It's Made' (factory tour) episode where the bottle making factory is cranking out six brand new beer bottles a second. BLAM BLAM BLAM - glowing bottles flying out in batches of six every second. Thirty dozen beer bottles a minute.
Flick.
On the other channel is a rather-breathless narrator discussing how "...3D Printing is the future of mass manufacturing; within just a few years everything will be made this way...", as the print head slowly goes back, pause, and forth, pause, back, pause, and forth, pause, back, pause, and forth, laying out 100um layer after layer of a crummy plastic bowl.
Flick: six beer bottles a second
Flick: one plastic bowl every 14 hours
Flick: six beer bottles a second
Flick: print head moves left, pause...
Flick: six beer bottles a second
Flick: print head moves right, pause...
.: The narrator is an airhead. It'll need about 18 Moore cycles (doublings of performance) to bridge the gap. Even at only two years per cycle, this promise is at least several decades away.
(Of course, it has its niche applications. No argument.)