"Absurdly low cost" won't work with the giant welfare system that is the DoD.

The OP is referring to real vs perceived (manufactured) threats, but you know that.

There are nations that have the outdated ideas of winning wars and not stimulating the economy ... for them the ideas of mass produced drones built at BOM, with some stolen IP from US are tempting.

Wasn't war always about stealing people's stuff or preventing your stuff from being stolen? I mean, my country had independence wars every generation for 800 years, but they were all about not getting our potatoes robbed.

The problem with such drones, is distance. Let's say Iran decides to take that approach. Then the question is: how far can they push those armed drones out from their operating bases. The answer is: not very far.

So no, drones saturating defenses isn't a serious threat to nations or regional strength, only to very specific targets that are nearby (eg an aircraft carrier & crew dumb enough to park off the coast of Iran, after they acquire such drone technology, and assuming the US has developed no defense for such).

The problems with such drones is not distance. When you remove the whole wetware, and the systems to keep it alive you can reduce the weight of the aircraft substantially.

Also it is threat for exactly the regional powers. Iran does not care about US, it cares for Iraq, Israel, Saudy Arabia, Egypt and Syria.

Not only you can reduce the mass of your aircraft, removing wetware also gives you ability to push it further in terms of speed and maneuverability. Current fighters are constrained by what pilot's body is capable of handling.