Thing is these are not mass produced, and are made for quality, not entry level pricing. The slowness comes from both the attention to detail, and waiting on suppliers since most of the rifle is assembled from existing parts. (Barrels, furniture, triggers, etc.)
Really the only main parts completely made by ATRS are the upper and lower recievers, charging handle system, mag and bolt releases, and optional muzzle devices, while the rest is either fitted to thier platform from a premade part or directly bolted on.
From this stand point, the only thing that could drastically speed things up is more machine time, and having an inventory of supplies to build the rifles on hand. I know Rick has invested in more CNC and individuals to operate them, but I think he is concerned about warehousing a ton of inventory for a rifle that could be made illegal at the stroke of a pen along with every other black rifle in this country.