<P> The series began development in January 2007 . HBO acquired the TV rights to the novels, with Benioff and Weiss as its executive producers, and Martin as a co-executive producer . The intention was for each novel to yield a season's worth of episodes . Initially, Martin would write one episode per season while Benioff and Weiss would write the rest of the episodes . Jane Espenson and Bryan Cogman were later added to write one episode apiece the first season . </P> <P> The first and second drafts of the pilot script by Benioff and Weiss were submitted in August 2007 and June 2008, respectively . Although HBO liked both drafts, a pilot was not ordered until November 2008; the 2007--2008 Writers Guild of America strike may have delayed the process . The pilot episode, "Winter Is Coming", was first shot in 2009; after a poor reception in a private viewing, HBO demanded an extensive re-shoot (about 90 percent of the episode, with cast and directorial changes). </P> <P> The pilot reportedly cost HBO $5--10 million to produce, while the first season's budget was estimated at $50--60 million . In the second season, the show received a 15 - percent budget increase for the climactic battle in "Blackwater" (which had an $8 million budget). Between 2012 and 2015, the average budget per episode increased from $6 million to "at least" $8 million . The sixth - season budget was over $10 million per episode, for a season total of over $100 million and a series record . </P> <P> Nina Gold and Robert Sterne are the series' primary casting directors . Through a process of auditions and readings, the main cast was assembled . The only exceptions were Peter Dinklage and Sean Bean, whom the writers wanted from the start; they were announced as joining the pilot in 2009 . Other actors signed for the pilot were Kit Harington as Jon Snow, Jack Gleeson as Joffrey Baratheon, Harry Lloyd as Viserys Targaryen and Mark Addy as Robert Baratheon . Addy was, according to showrunners Benioff and Weiss, the easiest actor to cast for the show, being that his audition was on point . Catelyn Stark was scheduled to be played by Jennifer Ehle, but the role was recast with Michelle Fairley . Daenerys Targaryen was also recast, with Emilia Clarke replacing Tamzin Merchant . The rest of the first season's cast was filled in the second half of 2009 . </P>

Average cost of an episode of game of thrones