I've got one that I bought about right years ago as a 200 yard deer rifle with little recoil after some back surgery. Seems like only a few fan boys are still into the catridge. I doubt it's worth much on the used market even if ammunition is still readily available.
You're thinking about the Grendel. Midway is selling 17 different 6.8 types of ammo, 14 different Grendel loads.