You can purchase foam kits that you spray yourself, somewhere around $2.00 per board foot, generally the largest you can get is 550-600 bf and will cost $750-1300...depending.
How are they defining a board foot? 1" thick for a square foot just like lumber?
I wonder what would happen if a person had a bus ready to be foamed and drove it over to where the crew was foaming a house and just brought up the subject over a beer at the end of the day lol.