Prokhorov math: value of investment in Nets has jumped upon move to Brooklyn, but how much?

Yes, the move of the Nets to Brooklyn has caused the team value to soar--another outcome not factored in as city and state agencies negotiated subsidies with the developer Forest City Ratner.

But how much?

The New York Post, quoting an unnamed investment banker, reports on the soaring value

In May 2010, [Mikhail] Prokhorov bought 80 percent of the team and 45 percent of the arena for $223 million. Of that amount, around $140 million was allocated for the purchase of the team, a source said.
Today, after subtracting $225 million in loans from its estimated $575 million value, the team’s has about $350 million in equity. So Prokhorov’s 80 percent stake would be worth $280 million — or double his $140 million investment.

Looking more carefully

If you do subtract those loans, to which Prokhorov contributed considerably, there's still the matter of $60 million in team losses. (More from NetsDaily.) The New York Times reported in 2009:

Although Prokhorov’s cash investment was announced at $200 million, he will also finance future Nets losses, up to $60 million, that are expected to accumulate before the move to Brooklyn, according to an executive involved in the transaction. The team has reported nearly $400 million in pretax net losses for its dozens of investors, including $129 million by Forest City Enterprises, Ratner’s Cleveland-based parent company.
Prokhorov will also be responsible for 80 percent of the $207 million in debt the team holds if the sale goes forward.

Also not factored in is this: the amount Prokhorov has promised to invest in the team as part of the deal.

The Nets have the league's third-highest payroll, as noted by NetsDaily's Bob Windrem: $81.8 million, prompting a luxury tax of at least $11.5 million this year, and perhaps double next year.

Still, Prokhorov now has most of the team and 45% of the arena. What enabled it? Government help.