Might be necroposting but whatever.
Your example isn't really the best considering that both Germany and Japan ran out of aircraft as well (or rather, could not match the production rates of their enemies).
As for the cost part, while eliminating the cockpit and pilot could save up on individual unit costs, there is still the issue of maintenance, storage, and rearming that tends to have fixed costs. Maintaining a large swarm fleet may end up posing unique logistical challenges as a result.
In addition, a big chunk of Gen 5 fighter costs comes from the hardware they're packing; they are basically flying super computers. While economies of scale can reduce the costs somewhat, a drone fighter would likely still run dozens of millions of dollars if it wants to remain competitive with other similar designs. And that's not even considering the effects of the esoteric bureacracy that haunts US procurement programs.