Typical costs: Interior paint itself costs anywhere from $12-$50 or more a gallon, depending on the quality. Painting a 12x12-foot room, both walls and ceiling, can require $25-$100 worth of paint, plus $10-$50 for primer, brushes, rollers, drop clothes and other supplies. For a 1,500-square-foot home, supplies run $200-$300 for average paint, and $400-$600 for higher quality.