This is companies use rebates instead of instant savings or just plain sale prices:
"My jaws dropped when I read over at PVRWire that TiVo saved $5 million from unredeemed rebates. TiVo has been giving out $50 and $100 rebates to new customers this past year but only 50 percent to 60 percent of customers send them in on time or correctly.
These rebates are $100 so I would think people tries harder to send them in properly and promptly. Now I wonder what percentage of people actually send in those smaller $5 to $10 rebates."