Things change with time. Lower-end "kit bikes" from relatively well established US brands have gotten cheaper, approaching $900 mark. Below this mark it's mostly imported junk with poor components, poor assembling and no support. For $1,000-1,300 expect better assembling and some support, though still poor components. This Stark is at the borderline, hard to tell much.
They are all "kit bikes", put together in China with readily available parts. Frame types like the one in Kickstarter or on Stark are shamelessly cloned, there is little to none engineering or ingenuity there. Batteries, motors, displays and cables are pretty much standardized, not to mention mechanical parts. As to the question how much ebikes manufacturers are making on batteries or motors - on $400 Stark probably none. This is a promotion, an expense they are willing to pay to enter the market.