Large billboards: range of $1,500 - $30,000 per location per 4 week period.
Medium billboards: range of $750 - $2,000 per location per 4 week period.
Small billboards: range of $300 - $750 per location per 4 week period.
Digital/video/LED billboards: range of $3,500 - $25,000 per location per 4 week period.
Wallscape: range of $10,000 - $50,000 per location per 4 week period.
Full billboard costs here.