Don Foreman writes:

I continue to assert that there is little power or energy loss in a
regulator.

Astonishingly, amazingly stubborn. Equivalent to belief in perpetual
motion, and denial of energy conservation.

Compressing air requires work.

Decompressing air spends this work, either usefully as through a tool, or
wastefully as in a restriction (aka, a regulator).

A regulator can be had to regulate arbitrarily close to zero output
pressure and any desired flow. The original uncompressed volume of air is
then released at near-zero pressure. Near-zero pressure times a finite
volume, yields near-zero work. Where did the energy go?