Comment by shilch

The presented solution does *not* loop inside bitcoin script itself, as you suggest, but outside whereby bitcoin transactions perform the state transfer. The machine runs for as long as someone pays for it (or it goes into accepting state) - which makes sense because if there was a one-time-fee for unbounded or potentially infinite runtime, you could create a program that never terminates. This can be compared to Ethereum where every step in execution costs fees and the caller needs to ensure that a sufficient amount of fees (gas) is paid.