I just attended the annual cartridge collector show in Castle Rock, Wa. and I can tell you that the value of your ammo is not in the 16 ct. box. Collectors love full, sealed boxes, and are quick to dump out opened partial boxes and sell them off peace meal. At the show I saw numerous examples of individual cartridges selling, and from condition and headstamps you could tell they'd all been in one box previously. Often the empty boxes were also on the table for sale separately too!
Ammunition as you describe varies by condition, and era. Paper patch factory ammo can get big prices, but not sure the .40-65 ever was offered as paper patched? I saw some people walk in the door to sell ammo and rarely saw it go more than $4-$5 per cartridge. Early boxes getting $20-$30. What I saw for selling prices was usually double what I saw the same people buying it for.