Free Laundry Soap

This laundry detergent is on sale at Target for $14.99. I found in the back by the Bodega section of the store. I scanned one found in the laundry soap section and they were ringing up at $20 plus. Anyway, this box ended up being cheaper than the sale price. It rang up at $9.98. So, what makes this free? I'll be mailing in a rebate form and they will be refunding my purchase price up to $15.64. Too bad the sale price didn't scan... If it did I would get $14.99 back instead of just $9.98. Other than that....a big box of Gain laundry detergent = FREE!