"Of course, this does not take into account the usefulness of morphs, only their number."

I don't doubt your theoretical numbers, but that's not how Poser works.

A cr2 only stores morphs at full strenght which are actually useful. The theoretical "trash-morphs" are all ignored.

A high res mesh can have more "useful" morphs than a low res mesh because it allows greater detail and you are not limited to predetermined edgeloops.

And once you go into custom morph creation with magnets or morphbrush, you have a lot more possible useful combinations with almost zero overhead, because only the finished morph is actually stored in Poser, not all possible combinations.

And of course, yes, a high res mesh uses more space for each morph.

But that's what injection morphs are there for.

:-)