Creating an artificial market around an artificial limitation that dumps cash into the government general fund is not what most economists would describe as "efficient allocation of resources".

It might create a local maxima around revenue per visa, but "google bought all of the H1-Bs to make life harder for Apple" is both an entirely foreseeable outcome, and one that has such a wide range of negative externalities that even in the context of the local maxima, it would be a challenge to argue of efficient allocation of resources with a straight face (if that argument is, in fact, the goal).