Can someone explain the logic behind the all-glass roof to me? I realize that it helps with headroom and the feeling of "spaciousness" in the back, but aren't the 2 main goals with the Model 3 range and cost reduction (of course both are related to each other)? Glass is heavy and expensive, so having all of that glass should decrease range and increase cost right? It just seems like a strange design choice from an economics perspective (from an aesthetics perspective, it makes a lot of sense). Tesla engineers are very smart people, so obviously there's probably something I'm not understanding. Anyone care to explain it to me?