Why is ammo so expensive?

I know ammo has gotten more expensive in the last few years and its still going up. I know there is more of a demand for materials, etc. And I know governments need more and more ammo for troops. However, even .22lr can be somewhat expensive these days. I always wanted a rifle in .338 Lapua but I looked at some ammo prices and I said screw that. 20 rounds can cost from $80-$120. Unless you get really terrible ammo, its quite pricy. Any other reasons why? I see no excuse for things being so expensive...