cost wise it depends on the vet and what you have done. For both of my horses that had the vet check I paid $120 I believe. Well worth it for when I was looking for a trail horse, the first horse I looked at, a beautiful red roan gelding, ended up having something wrong with his hocks. Not sure of the name she gave it, but he wouldn't be sound for long.
I just heard from the girl that bought him after I passed, and she was surprised that he was lame already. So thanks to my vet I have a sound horse instead of a lame trail horse :)