Part of it is that the NATO cartridges are in mass production and that brings the price down. For them, 9mm, 5.56, and still a lot of 308, and civilian demand for .22 and 12ga make the Big 5 and the bulk of ammo sales..38 special costs double what 9mm does if bought in a store.
And part of it is that the old revolver loads are mostly used in revolvers and you're ejecting undamaged brass into your other hand and it's easy to gather for reloading. The accompanying lever gun throws a bit further, ok! But shooting those calibres ends up going hand-in-hand with reloading them, so that further cuts into commercial ammo sales volume.
Being able to just buy a case of 9mm and not have to worry about reloading is part of the attraction of that calibre, but up til now 9mm has been totally semiauto.