Amazon Project Manager interview questions

It was 2 hours back to back interview. There were people in the virtual interview room. The interviewer was typing every response I told. I was asked several behavioral questions with many follow-ups. They also asked a short technical question.

They asked me four times throughout the interview process what my salary expectations were, and I was clear and honest with numbers, the same answer each time. They then had me attend over 5 hours of interviews (in fact, it was around 7 hours total). At the end, they offered me the job at a MUCH lower salary than the range I specified. And then they would not allow me to negotiate at all. I don't really understand why they couldn't have told me this from the beginning. The rate I was asking for was perfectly reasonable considering the position and my experience, and the rate they offered was way lower than my current salary was. I feel that wasn't very respectful of my time.