When i get around to it, im converting an old Marin rigid bike i have to 1x . Its their old Tange Prestige Team frame so a little effort and expense is worth it to me. Im using circa 2015 XTr derailleur and 11-40 11 speed cassette . I pulled this setup off my full squish daily driver when i switched to Eagle 12 speed on it and ithe parts have just been sitting in a box doing nothing
i recall weighing the cassette when i got it and it was close to a 200 gram difference compared to a cheaper steel 10 speed cassette . That was huge- and 11-40 is PLENTY of gear for a 1x 26er (was originally on a 29er)
And i have a XO-1 SRAM carbon crank with a 30t chainring i weighed recently, it was 475 grams. I weighed the xtr derailleur years ago and recall it was lighter than an equivalent Deore long cage i had laying around, but not earth shattering like the cassette and crankset difference. A triple chainring mtb setup can weigh well over 700g, so theoretically over a triple with a cheap cassette, im saving almost a pound using a carbon crank and xtr cassette, then deduct a little more for front shifter and derailleur
it wouldnt shock me if you saved 2 pounds over a 3x setup with careful parts selection