Joe, I am into the Remington 591 and 592 5mm. I assume that you are talking about the new Centurion rounds. They are about $20 a box of 50 at my LGS. The older original Remington 5mm goes for about $50-$75 a box around here. The new ammo has brought down the price of the old stuff in my opinion at gun shows. I have several rifles and enjoy them very much. I bought a 592 at Jaquas to hunt with and don't enjoy the tube feed as well at the 591 mag feed. They were ahead of their time with the round. It always amazes me that the 17 hmr took off and the 5mm didn't.
Doug, years ago, some of the rag writers called the Rem 5mm round a poachers dream giving the round/rifle a bad vibe. It got off to a bad start and went downhill fast. It's a potent little round and deserved better marketing. I don't think Rem cared much one way or other at the time?
I have 497 loose rounds in vacuum sealed packs I might sell since I don't have the 591, traded it off years ago.