No in the 70s there was not a huge emphasis on the no. of slams that players won at all. In the words of Chris Evert who skipped many Australian and French opens, 'no-one was counting back then'.
The slam count only mattered from the 90s when Sampras put a lot of emphasis on it. Why do you think Roy Emerson had no idea that he even held the grand slam title record for such a long time.
And yes prize money is incredibly important. Players don't just play for prestige and glory, they play to rake in the dough. Borg and Evert skipped the French Open to play in World Team Tennis which offered considerably more prize money. When the Australian Open draws were very weak, the prize money there was a joke, so top players understandably weren't willing to make the journey down there. McEnroe said that he was even offered appearance money to play at the Aussie Open one year.
The importance of the slams and the slam count increased as those events improved their prize money relative to other events.