Sure, but using 60kwh of a 75kwh battery lasts longer than a 60kwh battery would. Not to mention that Tesla's R&D to make a 60 kwh battery, an extra asmembly l

Sure, but using 60kwh of a 75kwh battery lasts longer than a 60kwh battery would. Not to mention that Tesla's R&D to make a 60 kwh battery, an extra asmembly line (or one flexible enough to produce both), extra inventory, testing, maintenance manuals, etc all has costs as well.