On Sunday, HBO's hit drama "Game of Thrones" will begin its eighth and final season.

The show's CGI dragons and epic battle scenes don't come cheap. Season eight will be the most expensive one yet, with episodes estimated to cost a whopping $15 million each, Variety reports. (A spokesperson for HBO says that the company does not confirm budget figures.)

The final season will feature some of the longest episodes in the series as well. The first two will only last about an hour each, but the final four are expected to run 80 minutes per episode.

The show's previous two seasons have been pricey as well: Starting with season six, a single "Game of Thrones" episode cost around $10 million to produce, according to an exclusive feature in the April 2016 print edition of Entertainment Weekly. That marks a budget increase of around $4 million per episode, up from the approximate $6 million earlier episodes cost.

Prior to season six, the most expensive "Game of Thrones" episode ever produced was season two's penultimate installment, "Blackwater," which featured an extensive battle scene and larger-than-life props, including a full-sized replica of a 14th century battleship. The episode cost HBO $8 million — and showrunners Dan Weiss and David Benioff had to push for the last $2 million.

"We had one really intense conference call with the HBO brass," Benioff told GQ. "It was awkward."

"I think we asked for $2.5 million. We got $2 million-something," Weiss added. "That's a lot of money in TV."

However, HBO understood that increasing the budget was crucial to getting the episode right. "We'd known for about a year that the ninth episode was going to be 'Blackwater,' and a disproportionate amount of our resources were saved for this episode in terms of time and schedule," Benioff said.

It paid off. "Blackwater" became one of the show's most admired and popular episodes, and it drew even more viewers to the series.

This is an updated version of a previously published story.

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