Where did you get your info about rim vs disc brake weights and costs?
Less material is needed for disc brake rims, so weight is less than rim brake rims.
Rotor weight may offset the lighter weight, making weight differences a “wash.”
Rim construction is simpler for DB wheels, and with less time and material required for construction they cost the same or less, right?
Zipp 404 Firecrest clincher
Rim brake: 1621g/set (claimed), $1076 - $1291
Disc brake: 1516g/set (claimed), $976 - $1050
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You mentioned rotor weight but left it out of the disc brake wheelset numbers (if I understand those numbers correctly). Add another 100 grams for rotor and weight is basically the same. Also add the cost of the rotor. As Tom A. always said, rim brake wheels have built in rotor. So you get the rotor for free!!
BUT wait, there’s more: disc brake mechanisms (hydraulic hoses, calipers, pistons, etc) will be heavier than rim brake system. Bare hubs also 60-100 grams heavier for disc brakes. Pro bike kit says rim brake bike is 500 grams lighter than disc version of same bike. Rim brake build will be cheaper than disc build all told.
I also don’t get how folks say disc brakes stop better in rain. My last gravel race a week and half ago was 80 miles in rain, mud, and wet sand. Over half the folks I talked with afterward said they lost their brakes as pads wore out. Mechanic (bike shop owner) at aid station sees me pulling in and sees that I’m able to stop quickly and almost silently on rim brakes, and he says, “there is a sensible brake design.”
Of course, I run alloy rims. However, for gravel (where deep section carbon rims don’t do diddly behind big tires), carbon rims don’t provide any overall weight benefits (with disc brake system) in comparison to slightly heavier alloy wheels with much lighter rim brake system.
But on the other hand, I have to admit problems: I’m running v-brakes which provide excellent stopping, but with minimal pad clearance, i have to keep my wheels very true. I’m probably going back to canti’s on next build, but they can be finicky.