There are a number of ways to go, but if your driving factor is
cost, then the bullet and the charge weights are what matter. Using these factors, the .22-250 will work well and perform as well as long as you are looking to save money. A 55-grain .224" bullet at 3600 fps will show less drop and less wind drift as a 150-grain .308" bullet at 500 yards. The .22-250 will be a bit cheaper to feed too using Midway pricing:
Sierra 55-grain SBT = $0.09 each
Sierra 150-grain HPBT = $0.15
IMR4064 @ $20/pound:
.22-250 = 35.7 grains = $0.11 each
.308WCF = 45.5 grains = $0.13
So you save eight cents each time you pull the trigger on the .22-250. You also get less recoil, and a bit less barrel life.
OTOH, the .22-250 is hardly protection against large bear. I hunted Kodiak most of the 27 winters I lived in Alaska, and I'm appauled that you considered it prudent to shoot a "charging" bear at 40 yards. I've been false charged many times, and they all stopped by 20-30 yards - not that yours would have stopped. I wasn't there and things may have been different in your instance, but this sounds too much like the fisherman who shot and wounded a sow on the Russian River this year because he "thought" it might
cross the river and attack him. This kind of thing gives hunters a bad name. If you really want bear protection, get a .338.
