During class this evening there was lot of discussion on rebates. Whether we like them or not they are part of the pricing strategy manufactures use to "push" their products. I came across an article that you may find useful (sorry it is lengthy) - http://www.cba.ufl.edu/mkt/docs/janiszewski/Rebate.pdf
As a Marketing Manager I have successfully used rebates in the past to promote a product, and yes sales during the period the rebate was offered did increase by 12%. One may argue if the increase in sales was directly related to rebate or other factors? Yes, most of the incremental increase was directly attributed to the rebate.
Happy reading