i think it really depends where you live and what you would do for the boarder's horse. Where i live, board can range from the low $300 mark upward to around $1200. The more expensive board has nicer facilities, full care board (will groom, tack up, cool down) have huge riding arenas. The facilities that are around $300 are nice, but it's like basic board, and there is usually only one or two riding areas.
Maybe look around at other boarding facilities and see what they have/do and compare it to yours.