It looks like it’s pretty much basic economic forces. As in demand is outpacing supply. It also looks like the Great Convergence of 2020 caused an unprecedented demand that the ammo companies can’t hope to keep up with. Finally, ammo companies are hesitant to build additional capacity due to the roller coaster nature of the gun/ammo market. Having seen the wild swings of the 2010’s, I can’t say I blame them.

H/t Tam