I am in Australia so this is in Australian Dollars per month.
Hay - $150
Shoes - $80-$90 or just a trim - $40-$50
Drench/wormer - $15 ( every 2 months or so)
Agistment -$15/week so $60/month
Fly repelent - $10
Tack - $20-$30
Total - approx. $345
This is for a mare who is NOT in work! If she was in work there would be extra costs for hard feed, supplements etc.
There are also the odd vet checks to pay for which can be very expensive!!
Hmmm.......now that i've done that I have this strange erge not to buy so much stuff at the saddlry that I don't really need!! Lol!