Are we to expect that they will really pay almost half billion for taxes?
Likely, they have no option but to pay that, and AFAIK, and that's why they can't just max out some contracts but still give their players a decent one.
Do Nba franchises really making that much money when they become champions?
Yeah, that includes ticket sales and other stuff like sponsorships.
(
https://www.investopedia.com/articles/personal-finance/071415/how-nba-makes-money.asp)