that all depends on how you shop with SIPS, you're pretty much SOL, you've got a handfull of companies pressing them out as fast as they can get the forests shredded to make OSB and setting the prices as high as they want. If you want SIPS... you pay the quoted price and might get lucky to get a 5%-10% discount if you're nice and buy $80K worth of them
If you stick to the more mainstream materials, the price is what YOU want to pay. Buy when stuff goes on sale, not when you need it, look for reclaimed insualtion, buy direct, second hand, etc.. it's all up to how crafty you get with it