proprietary
One of the big issues that i found with both the .408, and .416, is that for the time being both of the rounds are proprietary. This means that, that specific company is the only one that will product the ammo, making brass and loaded ammunition expensive.
from what I've heard Cheyenne Tactical spend so much money developing the .408 that they have to make their money back by pricing the rifles and ammo so high.
I agree with the 338 Idea, you can get a nice 338 lapua for significantly less than either of those rifles. and there are soo many options.
-barrett 98 bravo
-sako trg 42 and 41
-sig blaser tactical 2
-Accuracy International AW
-blaser lrs
-CZ high energy
-remington now makes a 700 in 338
-armalite ar-30
-mcmillan tac-338
-Only Long Range makes a semi-auto
-sig r93
those are just some of the more popular ones that ive seen, i'm sure that there are many more.