Q.... it isn't a technical debate, but a financial one. Tesla realizes cash flows are important, not to mention revenue (GAAP). So to that end, two things are occurring... first Order confirmation which move deposits on the balance sheet to revenue -- your order agreement states: by placing the order, your deposit is considered EARNED. This allows TESLA to book the deposit as revenue (there is no movement of cash, just a balance sheet statement). Secondly, things like Ludicrous and Autopilot are available in all cars and turned on by software. So those who order Autopilot at the time of order, they flip a software "bit" allowing auto pilot to work.... no expense since the hardware is already installed. Conjecture is the Ludicrous Mode is built into the current 90 Kw/hr battery ... so another "bit" flip on a P90D, gets Tesla $20,000 more in revenue. Following the same logic, whatever the margins on upgrades follow -- Premium Interior and Ultra HiFi. Whatever Tesla's margin is on these feature again represent more Revenue and Profit for the vehicle sold. The P90D has the larger motor and may also represent a larger revenue stream and profit as well assuming there is only a marginal production cost.
So can Tesla make a 90D -- yes. Can they make a P90D fully loaded -- yes. To pay for tooling, engineering, overhead, etc., Tesla has elected to build the most profitable vehicles first. So think of it this way.... the P90Ds are funding the potential to build the 90Ds. The same logic holds for 70Ds...why build the least featured vehicle now. Tesla is dedicated to become cash positive and earnings positive in 2016. Tesla can only borrow money for production for so long..... at some point, building out the Super Chargers, Paying for the new Paint Center, paying for the new assy line etc has to be paid for... either by borrowing more money or through sales. Tesla MUST increase returns from sales to generate positive income.