I would think that most of the cost of this F-35 is dealing with the problems caused by putting human in the middle.
Having multirole drones would lower the cost a lot, and it would actually likely increase its theoretical effectiveness because you wouldn't have a pilot scared for their life in it.
It would be so scary to go up against a drone multirole fighter, it could pull off the craziest multi-G moves, and it would be fearless.
There must be some technological reason we have moved to this yet.