I don't doubt this for a moment but I do doubt that the increase is coming from the manufacturers. I think the increase is coming from the middle man, whoever that is, because he knows he can get it.Sorry costs to LGS's are up. I've seen the invoices.
Manufacturers in any business do not normally increase prices for a temporary spike because their sales will drop while their competitors get the business. If Winchester raises their price per brick from $15 to $20 and Federal keeps theirs at $15 then the distributor will buy Federal, quote the Winchester price, and pocket the difference.
I am sure costs have risen as the demand for raw materials has increased and the powder and brass guys have had to raise their prices. More government regulations can increase costs to the manufacturer so maybe that could cause a slight increase but, in general, the meteoric rise in prices continues to be HUGE DEMAND rather than limited supplies. 4 months ago you had to pay $.90 a round for cheap .223 and now it can be had online for $.35. Similar situations were going on with most ammo as everyone in the chain took advantage of people who were willing to pay exorbitant prices for ammo.
The situation has eased off considerably in the past two months but is still a far cry from "normal". MY favorite LGS routinely has everything but .22LR bricks in stock at only slightly crazy prices. I think that we will see prices on even .22 drop back into some range of normal by Thanksgiving barring another mass shooting.