Subsonic (220 grain) 300 Blackout has >muzzle energy than 9mm +p (supersonic) and a far superior ballistic coefficient. It suppresses better (quieter) with better terminal ballistics. 30-cal suppressors are only a few hundred $ over 9mm cans. I sold my auto MP5 hosts and sears at what I believe to be the top in the market ($35K). It’s far cheaper to use an AR for a full auto platform.
It's rather more a bastardized carbine/pistol than anything else.... fires 9mm pistol round through a 3" barrel. My Taurus Millennial G2 does that for <$200. (Isn't that the "meat and potatoes"? The rest is all bells and whistles.) Starting at $1,600, that's a lot of loot for the "cool" factor.
Considering its effective range and cost, it's almost stupid. I'd be surprised if it were anything other than a huge flop. The more I ponder it, the more I'm astonished that Sig would even go to the effort to produce such a weapon... for that price, especially. But I'm not really into "cool" guns. (I'll bet that if you were to pony up for one of these, you'd be the only one on your block with it. )