Starship Prototype Unveiled
I'm slightly reminded of Sea Dragon[1].  That is, using fairly standard steal construction has the possibility to decrease costs even if it increases the net weight of the vehicle simply because it's so much easier to work with and cheaper than minimum weight high tech alloys.  Also, because both are quite big though Elon's ship isn't as huge as Sea Dragon was proposed as being.[1]https://en.wikipedia.org/wiki/Sea_Dragon_(rocket)