Kinda odd that they'd assume you're a novice or "in the industry" since you mentioned neither
I've seen 7n6 go for around .50 cents a round. Sometimes more, sometimes less
I had started a 74 build years ago and never finished, but had bought a pile of ammo for it. I keep waffling on actually finishing the rifle, shooting the ammo I have for it, and pitching it into the scrap pile once the ammo is gone, or selling all of it.5.45 is unfortunately dead