Maybe nobody will see this, but consider this thought experiment: You have a replicator like from Star Trek, which can make any computer that exists now, at zero cost (say it uses garbage you were going to throw away.) Presumably if you copied an Apple machine, it would not legally be a true licensed Apple machine, for the same reason that making unauthorized byte-for-byte copies of digital files does not create additional licenses to use them however you'd like. If Xcode's license requires licensed Apple hardware, it can't legally be run on that machine. On the other hand, FLOSS compilers could run on that, or on a free/libre hardware design that is not even in a grey area to replicate.

While the analogy is maybe a bit silly or different than what was originally said (interpreting "free of cost" more like "libre"), I think it illustrates a real difference that is relevant.

(Btw, I don't actually know Xcode's license -- maybe it only needs Mac OS for technical reasons, not licensing reasons, in which case it could legally and practically be run on any sufficiently correct Mac OS emulator.)

That's not his argument. His argument is that an apple computer is required for Xcode. An apple computer is a regular computer except that it costs more and comes with a bundle of software. Xcode is in the bundle. So... The price is indeterminable but definitely not $0. He hedged specifically against your reductio ad absurdem by mentioning the price difference.