Including complete rebuilds for the three Space Shuttle Main Engines (SSMEs), they were I gather somewhat needlessly too high performance/sports car types of devices.
In general, the Space Shuttle design was twisted by various unnecessary requirements (e.g. while the Air Force didn't want it, it could originally do a single polar orbit mission, which required extreme heat shield technology to land back at the same location while the earth turned underneath it. This was later mitigated by replacing a lot of those tiles with a ... glass fiber mat???), and to minimize development costs. Solid fuel booster you can't turn off were formerly considered to be unacceptably dangerous for manned missions, but they were the cheapest to develop.
Operating costs? Well, NASA post-Apollo makes the most sense if you view it as a public works project.... Low launch rates, especially post-Challenger after more people realized what an abomination it was, plus a huge fixed work force made it very expensive to operate.