Reports of the Justice League reshoots came recently, with Ray Fisher, Ben Affleck, and Gal Gadot set to reprise their role for additional filming with Zack Snyder. While there’s no indication as to whether Ezra Miller and Jason Momoa will follow suit, but the actors/crew will presumably need to be paid for their time. Ergo, budget.
Article source: https://www.cinemablend.com/news/2555417/the-snyder-cuts-reported-budget-for-hbo-max-is-seriously-expensive