I think that a lot of the buying ammo for a non-common caliber thing depends on where you are, and where you plan on being. While WallyWorld may well have those three boxes of .280 Rem, Mom and Pops stop and rob in Podunk may not.

Re reloading, a couple of things to keep in mind: Reloading gear is bulky (unless you happen to have an old Lyman 310 tongtool), and the components must be more securily stored than loaded ammo. A little moisture won't hurt most ammo, but it will wipe out powder and primers...