With all due respect.....some of the stuff you and I enjoy is likely puzzled over by others that might enjoy that "gizmo". It's a legal device per the ATF, so I'm okay with that. Having done some research on 'em, I doubt they'll last very long anyways - there's issues with how fast you release the trigger that can cause misfeeds/jams - and as ANYONE that's ever owned a FA firearm can tell you, the reality of ammo costs quickly outweighs the "cool of it.
But - if they wanna buy one, then let 'em. When they see how quickly a $20 mag of ammo goes, they'll change their minds!