Well, this is for my barn/area more or less because I don't know everything exactly and don't own a horse.
board: 500/month= 6000$
This includes stalls being cleaned regularly, 3-4 bales of hay per day, turn out whenever the weather is nice and it's not snowing/raining.
Extra supplements and special feed has be bought on your own I believe and brought to the barn if you want the stable hands to feed it to your horse.
Deworming: 15$ a tube.
Farrier starts at 40$ I think.
Some barns charge 700-800$ a month, but I'm not sure what it includes...
A ride a day keeps the worries away!