The best studio produced album of that era was Abbey Road. Makes sense that the Beatles had tons of cash and could afford it. From a technical standpoint it was groundbreaking.
That the wheels were coming off, that they were fighting each other, fighting to stay together, fighting to break up, and were still able to make such incredible music, is a tribute to their talent.
Maxwell's Silver Hammer was probably the first time I ever heard a synthesizer used in a song.