Rebates are not considered taxable income.  A recent IRS ruling which states that a rebate we provide you will not be considered income, but rather a lowering of the purchase price:

The IRS determined in Ltr. Rul. 200721013 that certain commissions received by real estate brokers that were passed along to their home-buying clients were neither reportable payments to the brokers nor gross income to the clients.

Source: RIA/WGL Journal of Taxation (preview) on Checkpoint