Not sure, but I have heard that the prices have come way down and are now only slightly above plywood.

no it does not. around here it is about $13/sheet. look else where I would say. Also get a price on the tape and figure out how much you need. Trust me, that will add up!

Builder Rebate on first time builders use of Zip Wall Systems and Advantech flooring ... $3 per sheet
http://www.advantechperforms.com/getting-started/rebates-incentives.aspx
http://www.advantechperforms.com/rebatefaqs.aspx

And just for an FYI ... LP TechShield (radiant barrier) as well as TopNotch 350, and FlameBlock all have rebates from $1.50 - $3.00 per sheet.
http://www.lpcorp.com/LP_Products/Roofs/TechShield_Radiant_Barrier/Product_Resources/
http://www.advantechperforms.com/rebatefaqs.aspx

And, you can get 2 squares of the Typar brand roof underlayment for FREE !! - http://fiberweb.typar.com/FreeSurround/. You can also get free marketing/advertising brochures and stuff from them about their house wrap ... http://www.typar.com/builder/programs/index.html?bl=main-builderPrograms&it=main-builderPrograms