Copies of, I think...

The valuer on Antiques Road Show is looking at an early edition of Pearl of Great Price (a Mormon scripture) which turns out to be worth $45,000 - $55,000. (Yeah. The woman who owns it was flabbergasted, too.) What's interesting to me is that he says to her:

"Pearls of Great Prices aren't all that unusual, but copies in these original wrappers are almost unheard of."

That pluralization - of both nouns, not just the phrase (Pearl of Great Prices) - strikes me as highly unusual, not to say weird.