OTOH, the moon, Mars and the asteroids could be settled for relatively little expense, in a fraction of the time and for a fraction of the expense as an interstellar voyage. If you're going to use Von Neuman machines for anything, THAT is the way to go.
Hence the Hawking quote I posted...
... is absurd, because Hawking is assuming that there's no location anywhere in the solar system suitable for human habitation and therefore extrasolar planets are the best logical alternative.
Hawking is simply wrong. The moon has sufficient resources for long term (if not permanent) colonization. Mars does also, especially if you project human expansion on a timescale long enough to allow for teraforming. Either location could be made permanently viable by harnessing the resources readily accessible in the bodies of our own solar system, many of which would be cheaper and easier to exploit than the miniscule cache of resources that exist in the Earth's crust. Simply put, with or without Von Neuman devices, if we spent half as much time developing the solar system as we spent on Earth, humanity could expand a fully developed and viable civilization across all eight planets and all 200 moons and dwarf planets.