The important word in my analogy was "invent." Given that the technology exists, lots of other things would happen—an emulation could be plugged into arbitrary "sensory" inputs, so a simulated universe could be created for it; that simulated universe would seem like an inviting prospect for those that do not wish to continue a life that mostly consists of sitting around on the Internet anyway, so more people (first-adopters) would upload as well, even if their "real" bodies continued separately; the large number of ems would provoke discussions of em rights, which would lead to internationally-funded medical programs to create two-way bridges between our reality and the simulations... and so on.

That's what I mean by "discontinuity": you can't give a cost-benefit analysis to something like a trillion dollars, because one trillion-dollar investment can completely alter the course of civilization with its knock-on effects.