I have no idea what engine count should have to do with argument: my rowboat has two engines (if my partner is coming along), yet I'm willing to part with it for below $ 150 million. It's also safer than most military helicopters and fighter jets, although I won't vouch for its behaviour in carrier catapult launches.

I believe the real argument is something along the lines off "yeah, those planes are BIG compared to the F-35", plus something that accounts for the helicopter. Maybe its unit price doesn't benefit from a split-off development process before? Or its expected sales volume is even lower?