Having your deck painted costs about the same as having it stained - $2 to $3 per square foot, on average. If your deck has lots of details or is very rough shape, the cost could be $5 per square foot or more.As a do-it-yourself project, painting is also relatively inexpensive. Budget just a few hundred dollars for paint and supplies.s a do-it-yourself project, staining a deck is relatively inexpensive. Budget about $25 to $30 for each gallon of stain. If you don’t already own one, plan to spend up to $200 to rent a power washer. Supplies such as brushes, rollers and tape will add $25 to $75 to the total price.