actually if the horse needs it, they ARE worth the money. my horse has crappy feet, and he has improved tremendously since i have had him on Biotin.
I was boarding him with a woman who stopped giving him his supplements, ( i asked to give them to him) but she got lazy, i knew he was not getting any b/c i counted the baggies. I moved him, b/c the care was minimal. after about 9 months when the hooves started to reach the ground level, they were a mess again, Brittle, could not hold a shoe, etc.. it took a while to get the supplements back into his system and for his foot to grow enough to see the improvement. Hoof supplements take a while, b/c you need the new growth to grow enough to reach the ground level to know if they work. if you only use them for a couple months, they are not going to show any improvement.
Horses that do not need the supplements can tolerate them, and will usually get a very shiny coat, if the hoof is already strong and healthy. if you don't need it, you might not want to spend the money.