This is why I think it was dumb to discontinue the 40kwh. The only saving grace has been that tesla is production constrained anyway.
I think the S40 would have the problem as the S60, too little value for the price. Consider the price per kWh.
S85.......$953 = $81000/85
S60.....$1183 = $71000/60
S40.....$1525 = $61000/40
The problem here is not that the cost of batteries is to high, rather the cost of the body (everything but the drive train) is too high. With such an expensive body, you have to match it with a really large battery to get a good value, a low total price per kWh.
If the supply constraint was simply batteries, then it should be recognized that smaller battery packs is the way to get the most cars per constraint. Consider this. Suppose you have 1GWh of batteries. How many cars can you make?
S85.....11,765 = 1,000,000/85
S60.....16,667 = 1,000,000/60
S40.....25,000 = 1,000,000/40
So had Tesla taken a path of emphasizing smaller pack versions of the Model S, it would have been able to produce as much as twice as many cars. This of course assumes that battery supply was the only constraint. So the fact that Tesla did not take this path suggests that the supply constraint is not the battery supply. It is something else.
I think the basic constraint is the overall cost and complexity of expanding per car capacity. The constraint is per car, not per GWh. Moreover, the Gigafactory is not going to resolve this per car constraint. Fortunately, Tesla is addressing this constraint. The have added a second line at the Fremont plant and have the potential to ramp per car capacity up to 2500/week.
This puts Tesla at a crossroad. They can continue to emphasize higher end vehicle and maximize gross margin per car, or begin to tackle affordability and go for higher unit sales. Does it make sense to maximize unit sales at the expense of profitability? Absolutely not, beacuse profit is the fuel that makes expanding capacity possible. Tesla cannot get to making millions of cars per year without a substantial gross margin to reinvest in growing capacity. What I would like see is just a modest move toward affordability and higher unit sales. Suppose we define two constraints:
1) Model S ASP not to exceed $100,000 and not to fall below $95,000
2) Model S GM not to exceed 33% and not to fall below 29%
Under these constraints it is posible to lower the base price and increase unit sales. Consider that options can be priced at a margin higher of 50% or higher and add to ASP. Pricing the D option at say $10,000, if uptake is 20% to 50%, this would add $2000 to $5000 to the ASP and add 1% to 3% to GM. This may well take ASP and GM above the my proposed constraints. This affords Tesla the option to lower the base price on S60 to bring ASP and GM back within target constraints. Essentially this approach leverages advancements in options offered to drive greater affordability and higher unit sales. When the D is unveiled, I hope the other thing is that base lrice on the S60 is lowered. Tesla can offer both.