There's no shortage, and there isn't going to be.
When ammo companies load ammo, they load in batches. When the current "batch" starts to sell out, they retool their machinery and load another "batch." Just like we handloaders do.
Sometimes, any particulay caliber becomes a little scarce, or actually "less abundant" just before a new batch hits the shelves.
If you're having trouble finding cheap .223, wait a couple of months, it will be abundant again very shortly.
BTW, this is a good reason to buy in bulk.