Lex Luthor, being the entrepreneur that he is, has a line of hair care products. They sell very well, at least at first. Turns out it's a bunk product, maybe even a front for a pyramid scheme. Maybe a bankrupt Clark Kent comes to Metropolis to expose Lex Hair Care?
At the climax of the story, Lex proclaims that his products are the best in the world; he uses them everyday for his luscious locks (lots of emphasis on the fact that he has the best hair out of anyone in the story). Then, in a very dramatic fashion, his wig is torn off!
It could all be an alternate explanation for how Lex loses his hair