Not true at all. Adjusted for inflation, most ammunition is about as cheap as it's ever been. .22 LR is really the sole exception, but it will come back down eventually.
If you're thinking in the context of cheap surplus ammo, you need to adjust your perspective. That stuff waxes and wanes, sometimes the result of politics, sometimes just because it runs out. 5.45mm 7N6 was about the cheapest centerfire rifle round we've ever seen, and an importation ban ended it. Various 7.62x25mm surplus loads were as little $0.08/rd a few years back; the surplus ran dry. You cannot calibrate your ammo price calculator based on imported surplus ammo, though. When it's available in large quantities because one nation or another is unloading huge stock, it's dirt cheap, but the price will skyrocket when the pipelines run dry.
Meanwhile, rounds like 5.56 NATO and 7.62x39 Soviet have held pretty darn stable, with a couple of notable market-driven spikes. When I bought my first .223, a mini-14, in 2000, I was paying $6-$7/box for for M193, could get as cheap as ~$225/case for brass cased and boxer primed ammo. Adjusted for inflation, $225 2000 dollars is $305 2015 dollars; brass cased and boxer primed M193 has been running right around $325/case until the M855 panic this month, and you could find it sometimes for under $300.
Also bear in mind that the early 2000's were the hayday for ammo; go back another 10-15 years, ammo was more expensive relative to income than it is today. I'm only 33, so I wasn't buying ammo in 1985, but I occasionally come across boxes of that vintage that still have price tags reflecting higher ammo costs than our contemporary market. I'm sure some other members may be able to post photos of 30 year old .45 ACP boxes with $9.99 stickers on them, what would amount to $21.70 today. Meanwhile, right now, one can go to Walmart and grab a box of Federal aluminum cased .45 for $14.97, brass cased for about $20.