I belive the liability plays into the cost some, its Insurance basically, and they have a guarantee/ warranty. Besides, have u priced 50 amp components, wire, plugs, etc., etc. That stuff ain't cheap. Copper is at least $2 a pound-scrap price.
If there was a "cheap" unit out there, I personaly probably wouldn't buy it anyhow.
Reputation is worth a butt load of $$!!!
MillerTime- Future Sabre Handler!!