Here in Colorado there is a lot of variability. I will say that I am super lucky to have gotten in where I board (thank to Countrygal's BF). It is pretty much the BEST value for actually good care that is not half way to Kansas.

Board: $200 month for "Community Corral" (Read turnout with free choice hay. No grain- that I have to do myself.)
Grain: $450 a year approximately.
Farrier: $40 per trim so about $300 a year
Wormer and Shots: $400 a year for wormer every other month, Teeth floated and shots twice a year with coggins.
Not including anything else such as supplements, fly control, lessons, and other equipment:it comes to about $3550 a year.