The foremost reason to use premiums on big game is to effectively guarantee an exit wound, especially with A-Frames. Exit wounds bleed and a blood trail greatly reduces the chance you'll lose an animal.
The cost of premiums is trivial compared to the value of a lost animal. Even if they only make a difference on a couple percent of shots, it's well worth it.
And I wouldn't hunt elk with a .243 either - that's the whole terminal ballistics part I mentioned. But a 6.5mm (pick your case) shooting 140-160gr A-frames or weldcores? Absolutely. Less recoil, a lighter gun, and higher SD than a .30-06. That whole efficiency thing...
