If you do all the labor and fab yourself, of course it's going to be less. But, there's not a lot of self-done SAS trucks showing up here either.
I think we would see quite a few more if someone came out with a kit. There are kits out there to SAS most other rigs just not ours.
If someone could package a parts kit for us (arms mounts, etc) for the most common axles used (80 series fronts) then i'd imagine they would sell fairly well.