Contractor/commercial models start around $1,000-$6,000 but can cost $10,000-$25,000 or more.Hiring a professional pressure-washer costs about $0.08-$0.35 per square foot (depending on local rates), but can go as high as $0.40-$0.80 a square foot depending on the amount and type of stains, dirt, mold or other problems.