In terms of pure value, it is probably fair, but only if Russell would extend before the trade. Westbrook is on another tier compared to IT, who I rate highly with the likes of Irving and Lillard, but none are of Westbrook's caliber. He is a top 5 NBA player and you obviously need to pay a premium for that.
In this scenario, we retain Crowder, Smart, and likely Turner. However, because he is an expiring, there is just no way you can sink that much into a possible one-year run - especially with the uncertainty in our front court.