Is worth the premium for a complete ambi lower
only IMO, at basically $900, for that money the only remotely comparable lower is the Radian A-DAC 15 (which doesn't come with a stock, trigger, or pistol grip and is $500 + blah in that state), but outside of that I'd argue you're better off parting an upper together to put on a KAC lower.
Basically $500 for a stripped + a comparable trigger + sopmod gets you to a roughly $900 pricetag for ambi-everything (not that I'd get a sopmod normally, but they're not bad stocks at all), so it's premium pricing for premium features, but not awful in that context, especially since Knights triggers may not be worth the pricetag they ask, but they are nice. Just not $400 and good-luck-finding-one-in-stock-ever nice; they make Geissele look like a good value proposition by comparison.