I'm seeing lots of ammo out there at high prices and mostly all in the high demand calibers - 5.56, 9mm, etc. On the other hand, hunting calibers are still harder to find and good luck if you're looking for something a little out of the ordinary. I've been looking for .257 Roberts lately, either loaded or just the brass. Not a chance. No one has it in person or online. I have some 7x57 brass laying around and it looks like I'll be using it to make up the .257.
My observation- my son and I both like to shoot.
My son likes to shoot rifles, "surplus" for the most part, but in our case that includes 30-30 (Winchester 94 lever gun). This being an old, classic "Western" gun.
So... run on guns and ammo started last summer; popular rounds like 9mm and .223 fly off the shelves (you can include 45 acp and 380 acp in this).
Manufacturers see this, see demand, and crank up production of those (9mm, 223 and such). Emphasis on those, other (ie "hunting" calibers) will be ignored... because they weren't in high demand.
*most people weren't rushing out to buy a .243 bolt action for self defense at that moment.
So now, we're seeing the results of the manufacturers. 9mm, 223, and such- now more available. Still pricey because hey, why not?, but it's out there.
Hunting calibers, which generally would be produced in small runs, weren't made in their normal timeframes, because there was such a continued high demand for the other stuff. So now, people are going to the shelves, and not finding what they normally would.
Going back to my son and his rifles- I found and bought 4 boxes of 30-30 (Federal), at Walmart, for $14 a box, last November. Wasn't in high demand. Seems to be extremely hard to find now. We're not interested in flipping or selling, at some point we will shoot them.
Argentine 7.65 Mauser ammo, same thing. Last year, found some PPU at reasonable price, found some surplus at reasonable price (as in, maybe about the same it had been in say 2018). Bought it, going to shoot it up eventually. Not available currently.
308, last year early on came across a clearance on ammoman, baggies of loose brass 308 fmj (Armscor), $20 for bag of 50. Bought a couple hundred. Purpose, shoot (at the time) through an Ishapore in 7.62 NATO, Armscor upon contact assured me they load their 308 and 7.62 NATO identically, that the rounds THEY MAKE would interchange.
You can go on and on, and draw the conclusion: big ammo run on popular calibers, manufacturers then focused exclusively on those calibers. As supply of other calibers dwindled, they weren't replenished.
We bought 'excess' because we plink in those, others might buy a box or two for express hunting purposes and didn't expect to need to buy more than needed that season. Now THEY feel the pinch.
Goes to show you, you SHOULD get 2+ years worth of what you need, even if it's not high demand. Limits of production dictate what gets made, and if you have something 10 million folks don't want right now, it won't be prioritized.