The real problem with buying ammo is keeping it fresh. Even if it comes in a spam can, there's no guarantee that it hasn't been contaminated. I store every round I own in sealed ammo cans. A flood or fire or tornado could hit and all of my stuff will still be usable.
A number of years back I had a sealed spam can of Korean 30.06. Sealed. I opened it up only to find that there were droplets of bright blue copper salts everywhere in that can. Bright robin-egg blue. The ammo sucked to high-heaven. I had at least 50% "click-bangs" which was really dangerous.
It took a while to figure out what had happened. Turns out that what did happen was the little Korean fella who packed my ammo can before it was soldered shut was sweating.....sweating a lot. His sweat dripped into the can and, after 4 decades, that salt water began to bother the ammo sealed inside. I ended up giving it away as components. Even the primers were affected.
Rome