A thirty second Superbowl commercial costs about $5 million, but the advertisements reach over 100 million people. The cost per viewer is a bargain but the inability to target a specific audience mean much of the advertising budget could be wasted on viewers who do no have an interest in the product being marketed. Most of the advertisements are for large brands and advertising focuses on brand recognition as opposed to marketing specific services and/or offers. These advertisers are typically large corporations and their Superbowl commercials are just a small part of their overall marketing budget.
These commercials are worth the return, publicity, and brand recognition generated by these commercials but they are not ideal for every business. Most businesses will see a much higher ROI from targeted campaigns at consumers and businesses who specifically fall into their target demographic. Targeted direct marketing and direct mail has a much higher cost per viewer, but focuses on a demographic that is much more likely to convert.
Another benefit is that Superbowl commericals have a longer shelf life. The 30 second spot gets played over and over again by news channels, blogs, etc, and they are always a topic of conversation. Similarly direct mail typically has a longer shelf life as they are viewed by who ever collects the mail then typically sit out for a few days and are perused by other members of the household.
Superbowl commercials are expensive but the cost per viewer is relatively low making the potential ROI high. Yet, these commercials are only beneficial for products with a national scope whose message applies to the majority of superbowl viewers. Most companies do not fall into this scope and a targeted direct marketing approach is often preferable and has a higher ROI.