The difference between the 70D and the 90D is greater than you think. First off, the 70D does not include the Smart Air Suspension. Second, many people who order the 70D will order as close to the base model as possible, so they will not get the upgrades package. Thirdly, if you look at the range, output and top speed of the 70D it is very likely that both motors are smaller than on the 90D.
My car comes in at over 110k before the destination fee or the taxes. The things I did not order are the ultra HD Audio, the towing, and the Performance option. I got everything else, and the only real difference would be the inverter for the rear motor, and the rear motor assembly itself. As far as trim goes, it has exactly what many of the P90Ds have. Therefore, I think as far as Q1 is concerned it has more to do with money than manufacturing efficiencies. For Q2 margin differences should be less important, because they will be producing a lot of 90Ds by then anyway. The only question is when will they start.