S & D will always be a factor. 41 magnum and 44 special ammo costs more than 44 magnum ammo because they are far less popular.Is it because of demand & supply?
6.5 C is a niche round and from what I've read, has little advantage over the much more popular 7.62 NATO cartridge unless you are shooting extreme distances.
6.5 Creedmoor vs. .308 Winchester
Both the .308 Winchester and the 6.5 Creedmoor offer all-around performance for a variety of hunting and shooting applications, but there can be only one winner. Petzal weighs in and compares these two cartridges for accuracy, recoil, and effectiveness on game.
What kind of ammo prices are you seeing?