Where do illicit artifacts usually end up? Is there a type of person who buys these? Drug cartels? Russian oligarchs?

I remember being in the Egyptian Museum in Cairo, the guide said in a large hall “Only one of these objects is a replica, can you guess which one?” I said “Unfortunately, I know exactly which one because I saw it in the British Museum a week ago.” I got a look.

They can presumably include the vast troves of paintings and other artwork still held by many supposedly respectable collections in completely progressive modern European and other cities, which were originally stolen by the Nazis and pilfered away to later appear in these places after the war. Much of that illegally in the hands of its new postwar "owners" despite ongoing protest from the descendants of those who died in the camps after having their collections confiscated.