It was set to be a flagship Amazon Prime Video series, with top Hollywood talent guiding what was envisioned as a major franchise for the ecommerce giant. However, cost overruns and creative differences are plaguing a series that has quietly become one of the most expensive shows ever produced.

Meet Citadel, a global event series from Avengers and Gray Man directors Joe and Anthony Russo and movie and television scribes Josh Appelbaum and Andre Nemec.

Multiple sources tell The Hollywood Reporter that differences in vision led to the exit of half the creative team and has forced the show — a spy thriller that is meant to launch local spinoffs — into a round of expensive reshoots.

Now, a seven-episode series that was already costing at least $160 million net, is adding $75 million, sources say, and is on track to becoming the second-most expensive show ever made. The spiraling costs and reshoots come in as Amazon launches The Lord of the Rings: The Rings of Power, which has the distinction of being the most expensive in television history, with rights alone costing $250 million and the cost of season one said to be at least $465 million.

The streaming wars have escalated budgets for shows and movies in recent years as companies try to one-up each other for streaming eyeballs. In the case of Rings of Power, it may have worked, as the show garnered mostly rave reviews that also praise the production value seen on the screen. While it’s too early to judge Citadel’s fate, the behind-the-scenes struggles show how the pressures of such as series can cause a break in a creative partnership — and how there seems to be no ceiling for spending in the search for marquee event series.

Citadel was a passion project for Amazon Studios head Jennifer Salke, who was looking for a big title to make waves. And she got it: An Avengers-style spy show, with spies from key countries who come together for the ultimate mission. And cooler still, the show would generate local spinoffs, with the spy characters having their own adventures on their home turf. India, Italy and Mexico were among the countries being targeted.

Citadel was set up and given a green light with much fanfare, commensurate with the talent involved. The Russo brothers, who would be executive producing, were hot off their blockbuster back-to-back Avengers movies. And Appelbaum and Nemec, part of the screenwriting collective known as Midnight Radio, were known for their acclaimed TV work and movies such as Mission: Impossible — Ghost Protocol and Teenage Mutant Ninja Turtles. The group was simpatico with the Russos, having a partnership that included a first-look deal with the filmmakers’ company, AGBO.

Game of Thrones actor Richard Madden and Priyanka Chopra Jonas were cast as leads, with the actors spending most of 2021 shooting the show, which wrapped in December.

It was then that the production team behind Citadel began to crumble into factions. According to sources, Amazon had some reservations about early footage, with the Russos, who were less involved due to a focus on their own pricey action project, The Gray Man, parachuting in. This brought about creative differences and led to two competing cuts, one pushed by the Russos, the other by Appelbaum and Nemec. As weeks rolled on, other project commitments had whittled down the creative camps to two opposing forces, Joe Russo and Appelbaum, who was the series’ showrunner.

Amazon chose to bet on the Russos, and days before Christmas, Appelbaum was let go. Says one source connected to the project, “What should have happened was Joe turning to Josh and saying, ‘Let’s get together and fix this’ instead of going solo. That’s not what partners are supposed to do.”

Appelbaum didn’t leave alone, however. Brian Kirk, known for his work on Game of Thrones and Penny Dreadful, and who directed five out of the seven episodes, also exited, as did line producer Sarah Bradshaw, among others.

Amazon had no comment on the budget or the exits. Two insiders noted that while the budget did hit upwards of $250 million gross, that included high COVID-19 costs, not factored in when the series was initially greenlit. Nor does it account for significant tax credits for shooting in locales such as London.

AGBO had no comment. WME, which reps Appelbaum and Nemec, also had no comment.

Another insider notes that across the television landscape, cost overruns and show overhauls have been occurring more frequently in recent years. “A lot of shows are suffering because executives are inexperienced for this level of production or dealing with artists,” says one TV veteran. Citadel’s scale was so complex it was shooting three units at once, according to sources.

It is unclear where and how the divergent visions for the show arose. One person familiar with the conflict says Appelbaum’s version of the pilot introduced the spies via a spectacular ski and hang-gliding sequence, setting up a spy-vs.-spy situation before flash-forwarding the story five years, with the heroes having no memory of their previous occupation. Russo’s version, according to this source, began at that five-year mark, jettisoning the action sequence.

In any case, AGBO, is now in charge of Citadel, and Amazon hired David Weil to rewrite the show and to give it more grounding. Weil is best known as the creator of Hunters, Amazon’s well-received Nazi hunting show that starred Logan Lerman and Al Pacino.

Thomas Sigel, a veteran cinematographer who had helmed two of the episodes of Citadel, officially took over directing the reshoots, which ran through the spring and into early summer. Sigel has an established history with the Russos. He was their director of photography on Cherry, which they directed, and on Extraction, which they produced. One source, however, says Joe Russo was very much involved with the shoot. The show is now in postproduction. No debut date has been set.

Appelbaum, Nemec and their Midnight Radio banner no longer have a first-look deal at AGBO. The duo retrenched away from TV and moved back into movie writing. Ironically, they are back in business with Amazon, working on a feature titled Heads of State that has Idris Elba and John Cena attached to star.

The behind-the-scenes events on Citadel affirm the Russos’ reputation of being perhaps the least spendthrift of filmmakers. Gray Man, starring Ryan Gosling and Chris Evans, cost more than $250 million and was the most expensive movie Netflix ever made. Even a small character drama, the Tom Holland-starring Cherry, became known for major cost overruns.

The filmmakers have earned enough goodwill to justify those budgets as the directors of some of the biggest films of all time with the Avengers and Captain America franchises. On streaming, Extraction stands as Netflix’s sixth-most viewed original film ever, while Gray Man is the fourth-most viewed original, according to Netflix.

The filmmakers also remain adept at finding companies to reach deep into their pockets, including for their latest endeavor, a sci-fi thriller titled Electric State. Like Gray Man, it is being made for Netflix, but only after a budget dispute with Universal, the project’s previous home, resulted in the studio putting it into turnaround after the directors made clear that $200 million was not enough for their sci-fi vision.