Ah, but while that was definitely part of the success, the reason portability was even interesting, was because it was free ;) You note yourself that the machi

Ah, but while that was definitely part of the success, the reason portability was even interesting, was because it was free ;) You note yourself that the machines came "free" with their own software- Unix would have (at first) had a hard time competing with the bundled OS if it was not free. In which case it would not have spread beyond the PDP-11. You might argue the machines are so expensive that "price is no object", but the major consumers of early Unix were (if memory serves) Universities.