I don't get the analogy. The Boom CEO explicitly stated that $100 tickets are not around the corner. Two or three generations down the line means four decades at a minimum, if we think one generation takes 20 years. Lots of things can happen in 4 decades, like: significant advances in ramjet engines, rotation detonation engines become mainstream, people get comfortable with windowless aircraft (so there's no need for drooping nose Concorde-style), airports could start being equipped with arresting wires, like aircraft carriers today, airplanes without the vertical tail fin become common place, stronger and lighter composites become available, and, who knows, maybe even some jets will start running on hydrogen rather than jet fuel (hydrogen having about 3 times more energy density per unit of mass). I have to admit the even with all these things, $100 per ticket to any place in the world still seems like a stretch, but I'm willing to give the guy the benefit of the doubt.