The Bulls lead the NBA in attendance this past season, and have been in the top 3 for the last 4 years. They have the money to invest in a superstar like Kobe.
http://sports.espn.go.com/nba/attendance
Kobe is signed for another 4 years at $20, $22, $23, $24 millions for those years, and consider the cost of mediocre talent is $5 - $10 million a year.
Here are the salaries for the Bulls from 2006-2007. Most of them are still controlled by the NBA salary structure for rookie contracts and will rise substantially in the next couple years.
In order for the Bulls to make a trade for Kobe, it would either have to include Ben Wallace, or they would have to sign a couple of their younger players to new deals and include them in the trade (sign-and-trade option used in NBA trades)--
Ben Wallace- $16,000,000
P.J. Brown- $8,500,000
Andres Nocioni- $3,950,000
Ben Gordon- $3,862,080
Tyrus Thomas- $3,260,760
Kirk Hinrich- $3,192,628
Chris Duhon- $3,024,000
Michael Sweetney- $2,696,956
Luol Deng- $2,614,440
Malik Allen- $1,803,600
Thabo Sefolosha- $1,679,280
Adrian Griffin- $1,475,000
Viktor Khryapa- $1,172,400
Andre Barrett- $744,551
Martynas Andriuskevicius- $664,209