The value of the Warriors increased by over 2 billion since Curry's arrival.
And I believe you've got the logic backwards - the argument isn't that anyone should be forced to pay Curry so much. Instead, if an employer wants to pay Curry, or LeBron or anyone else, that much to gain the value he adds to a franchise, they are forbidden by the league. That's a major restriction on a free market for teams to hire the most valuable employees.