New technologies usually have beneficial side effects. Such was the case with the F135 and F119 jet engines developed for the F-35 and F-22 (respectively) aircraft. New technologies from these two engines were applied to a new version of the F100 engine used in the F-16 and F-15 aircraft. The new F100-PW-229 EEP engine can now go for 6000 cycles (being turned on and off), compared to 4,300 previously, before requiring partial disassembly, inspection and replacement of parts (as needed). This will cut the costs of maintaining the engine (over its 30 year life) by 20-30 percent. These engines cost over $6 million each to purchase, and several times that to maintain before they are turned into scrap. The more rugged F100-PW-229 EEP can now go 14 years before requiring the inspection and refurbishment. Previously, most F100 engines rarely lasted nine years before getting pulled for the major inspection. The manufacturer of the F100 will be offering upgrade kits, so that when older model F100s are due for disassembly and inspection, the new components, that bestow the longer inspection cycle, can be installed. The first customer to get the new F100-PW-229 EEP will be South Korea.
Since it was introduced in 1974, over 7,100 F100 engines have been produced, and it is still being manufactured. These engines have spent over 22 million hours in the air. Much more has been spent on maintaining these engines, than in building them. The manufacturer gets a lot of that maintenance money, in the form of parts and service sales.
Until the 1970s, the engines were the most expensive component in a warplane, especially a fighter. Back during World War II, you developed a new aircraft by finding the most powerful engine you could, and designing an aircraft around it. In the last three decades, increasingly powerful, and expensive, electronics have displaced the engine as the most expensive component.