Verisign will be increasing the registry fee for .com domains and .net domains beginning July 1, 2010. These are the fees that registrars like GoDaddy, Register.com and others pay. Therefore the cost of a domain may be passed along in one way or another and typically by increasing the domain registration fee. It is advised that you renew domains before July 1. As to the cost Verisign said:

VeriSign announced that as of July 1, 2010, the registry fee for .com domain names will increase from $6.86 to $7.34 and that the registry fee for .net domain names will increase, from $4.23 to $4.65.

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Domain Traffic
Interesting fact about domains in general from Verisign:

As the economy and society becomes increasingly dependent on digital technology, it is imperative that investment in the underlying infrastructure, including .com and .net, continue to keep pace with the robust growth of the Internet and ensure its continued security and reliability. Over the last decade, the volume of Internet traffic and domain name system (DNS) queries on VeriSign’s global infrastructure has increased from an average of approximately 2 billion queries per day in the year 2000 to more than 50 billion queries per day today while maintaining 100 percent operational accuracy and stability for the last eleven years.