Information about the cost per graft can be found here:
http://www.battleagainstbald.com/bat...f_the_bos.html
It doesn't give the price per graft for the minimum 800 grafts for the promotion, but it does say that it is $9.50 per graft for 600 and $8.00 per for 1200, so with some extrapolation, you would be paying well over $7,000 to do the minimum 800 to get the 150k miles.