As of March 2008, the cost to register a domain name is less than $10. Moreover, the registrant has five days, the add grace period (AGP), during which any money paid is refundable. Even a minimal transaction cost is waived. The AGP was originally intended to allow legitimate purchasers to return names registered in error (with a typo, for example) at a time when the cost per domain was considerably higher.
Domain tasters make money from the practice in a number of ways besides selling profitable domain names. In some cases, they repeatedly register and unregister domain names, in effect obtaining the use of the name for free. A domainer may also register a large number of domains and then set up Web sites containing nothing but advertising links. The domain taster monitors the activity on each site and keeps the domain names that generate the most clickthrough revenue or produce the highest clickthrough rates.
In volume, even pages that are only registered for the add grace period can make a great deal of money. According to Jay Westerdal, the CEO of Name Intelligence, Inc., a Google AdSense partner was making $3 million per month from the practice -- after Google's cut.
Read the rest of the definition for domain tasting at WhatIs.com, including the approaches being considered to make the practice unprofitable.