I'd be careful using phrases like "steals a lot of watts" here...we're hardly talking 50 watts.
The SRAM 1x derailleurs have relatively strong springs, but the clutches don't come into play unless you've got an oval chainring, in which case clutch friction directly dissipates pedaling input. Even in that case, it's a relatively small number of watts.
Drivetrain friction is vexing because it's easy to feel small differences, but they still don't add up to much. Chains' apparent efficiency actually goes
up with increasing chain tension. Essentially, the absolute losses are somewhat constant no matter the tension. A rider putting out 100 watts might only see 90% drivetrain efficiency (100 watts output, 10 watts absorbed by the drivetrain), while the same rider on the same drivetrain making 400 watts would get 96.5% efficiency (400 watts output, 14 absorbed by the drivetrain). I'm making these numbers up, but the're a reasonable first approximation.
For the OP: DMF is still probably right that strong springs are the culprit. Other factors may include friction between the chain and your narrow/wide chainring. Doesn't AbsoluteBlack use a different tooth profile than SRAM? In any case, it seems pretty straightforward to swap out parts to find the exact cause.
If you're worried about spring tension, using the longest chain you can get away with will minimize the spring tension. Yes, a few more links would add weight (and maybe preclude you from using a smaller chainring with that chain) but you could get some of that back by trimming your rear derailleur housing.
I've seen a Friction Facts report that suggests the SRAM Red chain has more friction (a little over three watts) than a Dura-Ace chain when both have the stock lube applied. That same report suggests that you can get those three watts back by flushing the Red chain with solvent and re-lubing with something like Rock-N-Roll Gold or Finish Line Wet or FL Dry Teflon.
I understand why this bothers you, but rest assured that (a) you're not losing 50 watts or even 25 watts on your new bike, and (b) by removing the old lube and putting on something less viscous, you'll narrow the drivetrain friction gap.