Before, he was only making 44 million over 4 years, making arguably the most underpaid player in the NBA while making them hundreds of millions of dollars. [0]
Also, he only gets to take home half that pay - it's still a lot, but he doesn't quite have the contacts to do the crazy financial structuring that business tycoons and large publicly traded companies do to avoid income taxes. Famously Warren Buffet says that he is paying a lower tax rate than his secretary.
In all honesty, he's worth it, and probably underpaid. The Warriors' management and his endorsement partners pay without a peep. If his value were even marginally close to what they were paying him, there would be a lot of haggling going on.
[0] https://www.forbes.com/sites/vincentfrank/2017/06/06/nba-fin... [1] http://www.businessinsider.com/stephen-curry-salary-taxes-nb... [2] http://money.cnn.com/2013/03/04/news/economy/buffett-secreta...