There is a very human reflex to ascribe malice or avarice to pricing events--when they are not in the buyer's favor.
Perfectly normal and almost predictable.
High case prices deter case sales, which inflates supply (slightly) because a a perfectly natural response to high bulk pricing is to buy in smaller quantities.
Brand new buyers have no idea what "normal" prices are, that $40 for a box of 9x19 is unusual. They are only going to buy that one box, too. The 2-3 years, they may notice when a box is only $20, they may not.
If you are a person who already buys by the case, you are going to be more invested (NPI) in case pricing. If you suspect you are going to shoot a case off before, oh, December, you may make a weighted decision that $800 now is better than $900 later. And, it's all a dice roll, too. Case might be down to $400 by December, too.
Retail ammo is a "chain" too. The manufacturer sells to a distributor, the distributor sells to wholesaler/bulk retailer, and the retail shop is last in line. The manufacturer see nothing of the price increase. Neither does the distributor, either. The wholesaler, though is stuck having to pay a premium to the distributor, to answer all the retailer demands for product.
It's a double-edged sword for retailers, too. High prices can keep single boxes on the shelf, but they decrease custom from those fuming about "being gouged." And the retailer is stuck having to pay what the wholesaler has to demand, or have no inventory. No inventory will see your custom dry up, too. Can't win for losing.