All bike calculators I am aware of state the opposite, aero >>> weight, even at more moderate speeds. @mcneese.chad’s nice post gives a few concrete links that play with numbers. I think this is a case of feeling faster ≠ being faster.
On the latest Performance Process podcast episode with Dylan Johnson they gave a nice example (in the context of wider tires): a Ferrari driving over a bad fire road at 50 km/h probably feels faster than a Jeep doing 50 km/h, in no small part because the ride is harsher.
That has little to do with disc brakes and more to do with e. g. more intricate frames with integrated cable routing, electronic groupsets, integrated stem/handlebar combos and a dash of greed. A few years ago, Canyon was offering a 6 kg disc brake bike for not too much money. These days the price would likely be considered “affordable, mid-range”. Also the Aethos was and is UCI-illegal for the same reason.
Since most manufacturers want all, or at least the vast majority of their frames UCI-legal (i. e. above the 6.8 kg weight limit), they put the added weight to good use for aero features and the like.
And even then you’d likely still be significantly faster across the entire ride since you’ll eventually have to go downhill at some point.