David Fincher fans have no doubt been happy to pore over the filmmaker’s excellent new Netflix series Mindhunter over the last week, especially since he’s been gone for a bit. That wasn’t exactly the plan, as Fincher was already prepping his next project while doing press for Gone Girl in 2014, but that next project—a sprawling HBO drama series called Utopia for which he intended to direct every episode—unfortunately fell apart, and Fincher then moved over to Mindhunter.

Most recently the filmmaker has been attached to World War Z 2 at Paramount, but while Fincher says on the Empire podcast that development work continues on the zombie sequel with original Utopia creator Dennis Kelly, it’s not exactly a done deal:

“I worked on a show for HBO that didn’t see the light of day and at the same time was doing [Mindhunter], and then did [Mindhunter], and I’ve been working for about a year now with Dennis Kelly on World War Z… We’re hoping to get a piece of material that’s a reason to make a movie not an excuse to make a movie.”

Indeed World War Z 2 doesn’t yet have a release date and Brad Pitt is currently shooting James Gray’s sci-fi film Ad Astra, so it sounds like that sequel is still in flux. But during the lengthy discussion with Empire, Fincher did shed some light on why Utopia fell apart at HBO.

The series was based on a UK series of the same name, by Dennis Kelly, which follows a group of people that becomes obsessed with a graphic novel and finds themselves being hunted down by a mysterious organization. Fincher’s Gone Girl scribe Gillian Flynn wrote the scripts, and the cast was set with Rooney Mara, Colm Feore, Eric McCormack, Dallas Roberts, Jason Ritter, and Brandon Scott. The plug was pulled seemingly at the last minute, before production began, and Fincher says it all fell apart over less than $10 million:

“Utopia was something at HBO that I desperately wanted to do and I thought we had really, really good scripts and a great cast and we were getting ready to do that and you know it came down to $9 million. In the end, when you actually kind of lay it all out, $9 million in the scheme of things doesn’t sound like a huge discrepancy between what we wanted to do and what they wanted to pay for. But when you cut $9 million out of $100 million, 10% is not 10% in filmmaking. In filmmaking terms, you’re gonna have the same amount of drivers, you’re gonna have the same amount of accountants, you’re gonna have the same amount of costumers, you’re gonna have the same amount of stunt people. The only area that’s going to have to shrink by 10% is the amount of time that you have with the actors.”

And while Fincher admits the original UK series cost far less, he was trying to bring a tentpole feel to the small screen with Utopia and, by design, the series had to be shot chronologically—which is more expensive: