I’m not specifically familiar with how big farms prep for YHS. But I do know a lot about yearling prep, and I used that program to get my colt ready for FEH events and championships. Good prep helps a lot to make a young horse look competitive! BUT, it is a whole lot of work…honestly comparable to a horse in training…so I can see how big farms would charge about that rate.
When I managed a prominent TB farm, yearling prep started at $33/day. Horses were groomed daily, bathed weekly, handled by professionals and learned manners. Turned out at night, in during the day to keep coats dark. They were exercised 30min a day; alternating days between handwalking and walked/jogged in a Euro walker. Extra chubby ones spent 10 minutes working in a round pen. Some with growth issues skipped the walker (no tight circles) and were ponied instead in a big 20ac field with hills. It was a LOT of work getting the yearlings fit, but they (justifiably) looked like a million bucks after 90 days prep.
If you have the means and the time, you can certainly do the prep yourself. Start working 90 days out from show date, and handwalk your youngster 30minutes 5 days a week. If you have access to a pony horse, that’s even better! But don’t forget handwalking is still important for manners and to develop a loose, free, swinging walk at handlers shoulder. Add in spurts of jogging to teach obedience at trot, too. Once a week, do some work in hand on triangle turns. If you get bored handwalking, teach your youngster to ground drive…good exercise and great prep for starting under saddle later!