Matter of perspective. Musa’s “wealth” was from conquered peoples who retained most of it in their physical possession while he laid claim to it. That’s not too far off from being wealthy by today’s standards where almost no one has real physical proof of it other than data on a screen or a bank’s word for it.
But I’m the idiot who keeps saying that all currency is a shared suspension of disbelief necessary for civilization’s continuation, barely worth the cloth it’s printed on.
Replace “barely” with “not”.