I have 20 head at the time. (Yes I'm crazy)
I give all my own immunizations. If you give a 5 way shot, plus a shot for West Nile virus, which we have to do here as West Nile is around here a lot with all our mosquitoes. They cost me $35 for each shot, or $70/ horse per year. If I have the vet give the shots, it's $50 per shot per horse, plus the farm call of $60. Worming should be done at least 2 times per year per horse. I rotate wormers using an Ivermectin based wormer once, and Quest the other time. These vary in price, and I try to buy in quantity when there is a sale. But can cost from $9. to $13. The Quest is more expensive. Foals get wormed every 6 weeks until they are a year old.
Most years, baring an emergency, I can keep the vet costs down, but one unexpected issue can be pretty costly, and I am not lucky enough to have a vet in the family.
This year I decided to breed two mares to a World Champion stallion from Texas. ( his name is He's Stylin, you can google him and see what he looks like) Although they gave me a good deal for breeding more then one mare, the related costs for the vet to come and inseminate them has been just about $2000. I am not done yet with vet bills, as one needs to still be confirmed in foal. With any luck that will happen next week Friday.
I know, that was a chosen expense, But I wanted to give these two world class mares a chance to produce a nice foal, and they are related to my best show stallion. (mother and sister)
Sorry if I came across sounding glum, but I guess the point I want to make is that the greatest cost of owning a horse is not buying it, it's maintaining them. If you are lucky enough to have a large farm with all the machinery to make your own hay, or live in a place where there is mostly pasture year round you sure could do it more cheaply then I can. I'm way to old to do my own hoof trimming!