You'll be hard pressed to find a decent product in small quantities for less. If you want to buy in bulk, you can save some money. You can buy Volara for less, but it is really more of a flexible Styrofoam than what you are looking for. If you touch a lit match to it, watch out - burns like a mother. You might look on eBay for surplus Ensolite or something, but decent closed cell foam just isn't cheap.