Lol... this is the BARE minimum at a crappy facility that I'm trying my best to get out of.

Board (no care, no feed just a stall) $140 month = 1,680.00 yr
Food (alfalfa and grain hay... not including supplement costs, or shavings) $125 a month = 1,500.00 yr
Feet (trim no shoes.. 7 times per year) a little over 20 a month = $250 yr
Worming and Vaccines (administering most of it myself) $300 yr

That comes to about $3730.00 a year for one horse with no health problems. That total doesn't include bedding, suppliments, if I have him shod, emergencies, equipment, the time I spend cleaning his stall and measuring his feed, the delivery cost of hay, fly control, or the cost of gas to and from the barn. With all of that... there's no way to know.