Winchester factory ammo in 284 and 308 run at approximately the same velocities, but 284 ammo is always more expensive and harder to find. Other than the "cool factor" associated with shooting a 284, I can't see Why folks willingly pay significantly more $$ for the same level of performance.

X2842 = 150 grain PP at 2,860 fps.
X3085 = 150 grain PP at 2,820 fps.

I have thought that, with few exceptions, like the Savage 99 and Winchester 88/100, the 284 pretty much died the day that the 7mm SAUM and 270/7mm WSM came onto the scene.

Jeff