Why do you think maintaining the sense of free will is evolutionarily costly? If anything, to me, it seems like a heuristic shortcut that is imperfect but is useful most of the time, and saves resources overall.
As a close analogy, we've all said something like, "My car wants to pull to the right." Nobody claims the car has free will, but "wanting to pull to the right" is a useful way to both communicate and to think about it. What is is in the car's makeup that causes it to want to pull to the right?
There are plenty other examples where people have false beliefs yet still cling to them. If you ask drivers if they are better or worse than average, about 10% will say worse. My point is, having false beliefs doesn't always exert a strong evolutionary pressure.
As a close analogy, we've all said something like, "My car wants to pull to the right." Nobody claims the car has free will, but "wanting to pull to the right" is a useful way to both communicate and to think about it. What is is in the car's makeup that causes it to want to pull to the right?
There are plenty other examples where people have false beliefs yet still cling to them. If you ask drivers if they are better or worse than average, about 10% will say worse. My point is, having false beliefs doesn't always exert a strong evolutionary pressure.