I honestly have no idea how it can weigh that much. Unless that weight they gave is actually what it would weigh once assembled with the knuckles/brakes/etc. Which actually would be a pretty reasoable figure to give, as far as actually providing a useful number for comparison between the axle options that are out there, assuming you realized that's what they meant.
I find it a little annoying that the other axle builders seem to be less than forthcoming with what their products weigh. Currie offers no useful information on their D44, other than they added 14 pounds to the center section casting over the stock JK, and they use 3x.375" tubes. I'm not interested in their product, but I would be interested in it as a comparison. Likewise their 9" front, which the main point they make of going to it over a comparable "cast center section axle" is that it would possibly save about 50lbs of weight, but again they offer no number of what the total weight is.
I'm still trying to determine what will be my Goldilocks axle. D44 with normal outers, D44/D60 hybrid (I realized I can use the Cs off the 04 axle with the 3.5" tubes a lot easier than the earlier ones), or just take the 96 D60 and cut it shorter/shave the shit out of it, and put the 04 outers on it. I haven't actually bought anything for this specifically yet, but I have a 77 F-150 D44 that I can snag (solid tubes, no cast shit) that combined with Snowracer's D44 would make a complete one. The D60s I already have and I have no emotional attachment to either.