I buy human biotin tablets on Amazon and it costs me 5c for 10mg. I haven't looked at every horse supplement in existence, but they seem to be more expensive. I also supplement with copper and zinc. I use the Uckele powders, but they smell bad and I wouldn't be surprised if a pickier horse didn't ea...

I don't think it would bother me that much, depending on my goals. The horse is older and still sound under the workload I would be expecting, which is the biggest factor. I would definitely use this as an opportunity to negotiate the price down though.