Alibaba Co-Founder Joseph Tsai is buying a 51% stake that he doesn't already own in NBA's Brooklyn Nets and its Barclays Center arena from Russian billionaire Mikhail Prokhorov. Reports said Tsai paid about $3.5 billion, including debt, for the team and building. Tsai, who is worth about $10 billion, acquired a 49% stake in the team from Prokhorov last year.