Definitely a big number. Jordan Brand - counted separately from Nike's other lines - captured 58% of all basketball shoe sales in the US in 2014 (in dollar terms). Keep in mind there are dozens of Jordan Brand shoes now (whereas once upon a time it was one specific shoe, the Air Jordan), with other major players endorsing under the label (such as Carmelo Anthony).

It's apparently also booming in China:

http://fortune.com/2015/10/23/nike-air-jordans-china/