The Titan II/III/IV family (derived from the ICBM family of the same name)1 were the premier U.S. expendable launchers for much of the late 20th century, being the most capable expendables in the U.S. inventory from 1973 (with the retirement of the Saturn V) until 2002 (when the Atlas V and Delta IV entered service). They were also some of the most-expensive-per-unit-capability launchers ever put into service, causing them to be used almost exclusively for military satellites, along with twelve mostly-manned Gemini flights and a handful of experimental and science satellites; due to the launchers’ high cost-density, only three commercial satellites were ever launched by Titans, all of them by the unsuccessful Commercial Titan III variant in January-June 1990.2 Even the military, with radically-different launcher-selection priorities from commercial customers, found the high cost of Titan launches to be a serious hindrance, leading to the Titan family’s eventual retirement in favour of the newly-developed Atlas V and Delta IV.
I’m at somewhat of a loss as to why the Titans’ cost-per-capability was so high. One seemingly-obvious explanation would be the considerable handling difficulties resulting from their use of highly toxic and explosive hypergolic propellants (requiring extensive protective equipment and garb for the workers)... except that the Russian Proton and Chinese Long March families both had long, profitable careers as commercial launchers (indicating that their cost-to-capability ratios were acceptably low), despite using hypergolic propellants themselves, and, thus, requiring at least Titanesque degrees of expenses to mitigate the hypergols’ handling difficulties (probably considerably greater, in fact, since launches out of Baikonur or Xichang or Jiuquan or Taiyuan drop spent stages over land, incurring large cleanup costs when the incoming stages are hypergolically-fuelled, while launches out of Cape Kennedy or Vandenberg drop their stages harmlessly3 in the ocean).
So why were the Titans such expensive rides?
1: The Titan I was used solely as an ICBM; the Titan II pulled double duty as an ICBM and a space launcher; and the Titan IIIA, Titan IIIB, Titan IIIC, Titan IIID, Titan IIIE, Titan 34D, Commercial Titan III, and Titan IV served as dedicated space launchers.
2: The Commercial Titan III carried a total of five payloads in its four launches, but one of the first two (the payloads on the first CT-III launch, just after midnight on New Year’s Day 1990) was a British military satellite, and the last (launched in September 1992) was the NASA Mars Observer probe.
3: Harmlessly to people, that is; probably not harmlessly to the local marine life, but said marine life generally lacks the ability to lobby the government or sue the launch provider to get them to stop dropping spent rocket stages in the ocean.