Found on a website called Revenues from Sports Venues, the naming rights for arenas and stadia around the country, what was paid for the rights, and the length of the agreement. (That's an Adobe Acrobat PDF file.)

The nearest comparable arenas are the Ford Center in Oklahoma City and Alltel Arena in Little Rock. Alltel bought its rights for $7 million for 15 years, while the Ford Center naming rights went for $8.1 million for 15 years. The best deal I could find for an arena without a major league team was the $14 million Qwest paid for 15 years' naming rights at Omaha's arena.