I don't think it's just the shell. Looks to me like they did all of the interiors as well. As impressive as 90 hours is to do it (which I am by no means taking away from), it would be interesting to know how long it took to pre-fab all of the components. I'm guessing at least a few weeks. After that, it all comes down to people power. You put 100 guys on a project, it takes them 5 months. You put 1000 people on it, it takes them 5 days.