They are not especially light, and don’t need to be. They simply have to be reliable.
This Thought prompted me to weigh some of my wheelsets. I decided to weigh the front wheel since the gear cassette makes quite a difference when the ratios are not similar.
•CX disc with cross tyres: 1.83Kg#
•Raleigh disc with Schwalbe: 1.69 Kg
•Shimano Deore with Mavic A319 rims: 1.55Kg
•Shimano STX with Alexia: 1.26Kg
•Shimano R500 wheelset:1.23 Kg
•Mavic Aksium: 1.21 Kg
#These wheels are currently fitted with Slime inner-tubes which are considerably heavier than plain tubes.
Simply putting wheels on the scales is naive, the rotational momentum is often more important. I expect the CX wheels will fare worst on this score too. But with 11 punctures in their first month, I see no choice. It looks like both disc wheels have heavy hubs, but I am not troubled by that.
As expected, the Aksium came out best, but not by a huge margin.