Doesn't it seem obvious that both processes and supply costs tend to improve over time? (this isn't Tesla specific actually)
A couple of simple examples:
- battery costs (they have been on a downwards trend for a while, and expected to keep falling)
- production/assembly line costs: initial hiccups are expected and costly, and as you fix them and learn to optimize your production, your costs also decrease. The rejection rate starts dropping, and rework costs also start dropping.
This is true of pretty much any production: you get better at it as you go, and generally your supply costs also decrease. As you get out of the ramp-up "hell" you start producing a lot more, which starts giving you economies of scale.
Lastly, innovation also offers improvements that can give you another knob. For example, the motors in the M3 are now being ported to Model S to improve the range. This gives an option to either offer a higher range, or keep the range the same but put in a smaller battery (where the savings are going to be). I expect incremental improvements in M3 to have a similar type of effect.
I consider all that "work". I imagine it will lower the production cost, given the same spec. That translates to profit, if the price point is kept the same.