Anywhere from $100 to $500 depending on what you are asking for.
I personally don't get them. I do however show them to my trainer first. The reason I don't get them is because first off any vet can find a reason to fail a horse and that is for their own liability purposes, which means you'll never get a 100% sound out of it. There will always be a "You could see some arthritis in this area years down the road" type of comment. But you will get a "today the horse is in good health" comment.
I don't not believe in them... I just don't get them... Although If I were paying 10k, I might get one....not srue though....