YUP, gets expensive. I decided to consolidate calibers, but it didn't work out.
Now, I keep mags, ammo in huge store in .223/5.56, .45acp & 12 ga. Anything outside those 3 are just handy firearms with 2 mags & 500 rds of ammo being sufficient.
I consider my rifles/ Handguns/Shotguns in the above calibers, my 2nd Amend weapons and have ammo & mags accordingly.
40- 30rd mags per AR or subgun, 6 mags per .45acp & 4k shell of combat 12 ga on hand seems adequate for me. Other firearms are just handy guns and no-worries beyond SD on those.