Paramount Pictures/History with Star Trek/Acquiring the Original Series

Viewed as a commercial disappointment at the time, Gulf+Western initially wanted to exclude Star Trek from its purchase of Desilu. Desilu executive Herb Solow later stated, "Paramount didn't want Star Trek, because it was losing too much money each week and didn't have enough episodes to syndicate successfully. That was a wise business decision at the time." Nonetheless, Lucille Ball insisted on selling her company as an intact entity – excepting her own hugely popular Here's Lucy show – which forced a reluctant Paramount to also accept the legal and financial liabilities for the unwanted property. (NBC: America's Network, p. 218)
One week after the acquisition and alarmed by his financial audits, Gulf+Western founder, co-owner, president, and driving force behind the acquisition, Charles Bluhdorn, called one of Desilu's former negotiators named Ed Holly, utterly aghast. Holly recalled, "Just a week or so after the merger, when Bluhdorn had started seeing the cost figures, he called me in the middle of the night. All I heard was 'What did you sell me? I'm going to the poorhouse!' I said, 'Charlie, you must be looking at Star Trek and Mission: Impossible. Those shows are costing almost to the dollar what our projections showed they would cost. You and your people made the judgment that that was all right." (Desilu: The Story of Lucille Ball and Desi Arnaz, 1994, pp. 297-298) 
Although he had been known as a formidable business tycoon, Bluhdorn's exchange with Holly betrayed that he and his financial subordinates did not have a thorough understanding of the motion picture and television business. Bluhdorn had only become a "Hollywood Mogul" less than a year earlier when he had bought Paramount Pictures on 19 October 1966 and was not, in the least, reassured by Holly's assurances. Bluhdorn decided to visit the set of Star Trek in person to witness a day of production for himself and found it to be an underwhelming experience. What he saw on that day made him highly skeptical but, even though it was his prerogative as the temporary chairman of the board of Paramount Pictures, he stopped short of actually ordaining the series' cancellation. Ironically, it was the immensely popular The Lucy Show that got canceled immediately when its star performer, Lucille Ball, left the very next day, directly after the ownership transfer ceremony on the Desilu lot. Emphatically declining to work any longer on her own creation under new ownership, she immediately founded a new production company, Lucille Ball Productions, to the very specific end of producing a revamped version of her popular show, Here's Lucy, which enjoyed an equally successful six year run.
Instead, Bluhdorn had a small army of Paramount and NBC financial executives and accountants descend on Star Trek to go through the finances of the production with a fine tooth comb. Inevitably, this resulted in more severe budget cuts and creative meddling from these businessmen.
This interference eventually turned out to be the impetus for the subsequent departure of the driving forces behind the series which included Solow, Gene Roddenberry, and, eventually, Robert H. Justman. (Inside Star Trek: The Real Story, 1997, pp. 360-et al.) These defections only served to reinforce the decision to cancel Star Trek as soon as possible but fan letter-writing campaigns convinced NBC to renew the series twice.
Despite NBC's and Gulf+Western's financial experts' grave concerns about Star Treks high production costs, the final decision to cancel the show was not made by television network NBC until the end of the series' third season, reportedly leaving the entire production at US$4.7 million in debt. (Star Trek Creator: The Authorized Biography of Gene Roddenberry, p. 399) 
Due to its original contractual obligations, net profits (non-existent at the time) were to be shared between the studio (26⅔%), Roddenberry's production company Norway Corporation (26⅔%), performer William Shatner (20%), and NBC (26⅔%). Due to its losses, Paramount offered Roddenberry the opportunity to obtain the Star Trek property for US$100,000-$150,000 in 1970. However, Roddenberry was unable to raise this sum on his own so the ownership of the property remained with Paramount. 
This turned out to be extremely fortuitous for the studio, and as Solow put it, "History would show that Gulf & Western's purchase of Star Trek alone, the low-rated, money-losing second-year series on NBC, would become one of the most spectacular business moves in entertainment history." (NBC: America's Network, p. 220)