I thought of you this for while now. I prefer to look at package cost as fraction cost of whole car. Model X 75D->100D is 17k more for 25kWh. Model S 75D->100D is 23k more (but with air suspension bundeled). So if we assume Model S 25kWh upgrade cost 17k of 74.5k => 1/4.3824th of price of whole...