This type of spray foam offers the specific benefits of continuous insulation interior wall cavity fill and unvented attic applications.
Attic closed cell foam insulation.
There is 300 difference there but the cost they give you is about a third difference and open cell foam at 12 inches will not give you the performance of 2 inches of closed.
Open cell foam weighs 1 2 pound per cubic foot and closed cell weighs 2 lbs per cubic foot.
Insulating value and strength open cell foam has an r value of about 3 5 to 3 7 per inch while closed cell foam has an r value of about 6 per inch.
Closed cell foam can also increase the racking.