Price of hair really varies depending on the quality required. If it's being mulched down to make the commercial solar panels, then it would likely cost next to nothing. However if you need high quality, long undamaged strands it's going to cost you, because you're going to be competing with an existing market (wig, mannequin and certain dolls are typically made with all real hair), which will drive prices up significantly.
I believe the ultimate ideal for this would be to make the hair easily replaceable by a person. Quite literally grow your hair X inches long, cut, hold out straight and clip into place. This is likely to be sold out in poorer countries where people haven't handled technology and need a simple way to maintain it. However the countries that would typically require this are somewhat blessed by the near perfect black of their hair, because blond hair has little to no melanin and would be useless, even brown hair would reduce efficiency greatly.
I believe the ultimate ideal for this would be to make the hair easily replaceable by a person. Quite literally grow your hair X inches long, cut, hold out straight and clip into place. This is likely to be sold out in poorer countries where people haven't handled technology and need a simple way to maintain it. However the countries that would typically require this are somewhat blessed by the near perfect black of their hair, because blond hair has little to no melanin and would be useless, even brown hair would reduce efficiency greatly.