I worked for ten months for a bank, in a team of about ten people (mostly external consultants, so pretty expensive), to build some new feature of their customer website. The feature had been proposed as part of some internal initiative and was pretty much useless. From the start it was clear that the project manager hadn't understood at all the concept of what we were asked to build, and even after several months and a lot of explanation he was still proposing stuff that showed the same misunderstanding of the concept; the feature consisted of all of three or four views, but the designs were constantly changing (despite being almost childishly simple), the huge monorepo was so badly set up that each hot-reload took several minutes, and the backend needed to go through an insane amount of bureaucracy.

In the end, we managed to produce three working web pages, and then the team was disbanded and the project shelved. The whole thing might have costed the company a million or more. Pretty sad, but now I tell people that I know why the interest rates of their bank accounts are zero.