Basically, it's a rebate.  You buy the product, and send in the coupon that comes with it as well as a proof of purchase to ensure you won't return the drive.  You wait about 6 to 8 weeks, and you get whatever money the coupon is for.  What it boils down to is...most consumers are lazy, so they sell a ton of drives and hope to get only a few rebate coupons in the mail.  One burning question is...If they wanted to sell more drives, then why didn't they just reduce the price instead of playing the rebate game?