I must be in a lower tax bracket - if I bought 2k in components for every rifle I’d need a much larger garage.
For an elk rifle, it gets sighted in and one box of ammo goes along on the hunting trip, so 100 bullets would last at least a few years. Same for the backup elk rifle. The second and third backup rifles don’t need much.
A deer/antelope rifle gets shot more with multiple zero checks, but 50 rounds a year would be all it really needs. Same for the backup rifle. The second, third and fourth backup rifle not so much.
A small varmint rig is different and it really needs at least a few hundred cases and 1000 bullets. Same for a plinking/training rifle. Same for any kind of competition rifle. A coyote rifle needs a lot less.
I have a 458 win mag, but I’ll never burn out the barrel - same for a 375 - one box of ammo is enough for the longest range session. Same for the guns that rarely get shot. It doesn’t make sense to load up 100 rounds for a rifle that may not get shot at all this year.
It all depends on how much you shoot, what you like to shoot, and if you like to reload fewer cases more often, or more cases less often.
As for how long a barrel will last, the 22-250, 243, 270, 6.5 prc, 300 prc, 7 mag type of guns will be lucky to make it much over 1500 rounds. 6 br, 6.5 creed, 7mm08, 30-06 maybe twice that. 223, 30 br, 308 maybe 5k.