A new study suggests that big endorsement deals and long careers combined are what make many professional athletes wealthy, not their lofty salaries.

Wealth-X, a service that provides analytics for high-net-worth private banks and luxury brands, released a study Tuesday that ranked wealthy professional basketball players, following last week's NBA Draft. The group, which defines high-net-worth individuals as those with assets of $30 million or more, found that 75 percent of the wealthiest NBA players who played in the recently completed season have been playing for an average of 15 years and were already playing in the league by 1998.

Kobe Bryant, drafted in 1996, ranked highest with a total net worth of $220 million.

"Bryant, who will earn $27.85 million in the 2012-2013 season, continues to draw the highest salary in the NBA," the study reports. "This is supplemented by multimillion-dollar endorsements with Nike, Coca Cola, Turkish Airlines, Mercedes-Benz, Lenovo, Panini and Hublot."

LeBron James, drafted in 2003, ranks below 17-year veteran Kevin Garnett, who was drafted in 1995. Garnett's net worth is $190 million, spurred in part by a $4 million deal with coconut water brand Zinco and another with Chinese sportswear company Anta.

James' net worth at the time the study was conducted was $130 million, and as the star player of this year's championship team, the Miami Heat, his endorsement deals are likely to increase.

"Against the backdrop of the NBA Draft last week, it is interesting to explore the correlation between talent, performance and net worth that is revealed in this ranking," said Wealth-X President David Friedman. "It provides a window into the value that society implicitly places on the skills of these professional athletes and the role of entertainment within our culture."

Tracy McGrady, who has not been a starting player for a number of years yet was drafted back in 1997, made the study's top-10 ranking in the No. 10 spot with a net worth of $80 million.

The study connects longevity and endorsements because familiar players can continue to accumulate endorsement money beyond their playing careers.