Its funny that I've been playing pins / vids since I was tall enough to see onto the screen / playfield.  My whole life I can only remember ever seeing 20c games...Never a 10c machine anywhere.

When the DMD's came out, it was a $1.00 for a 3 ball game

Yes, definitely 20c a game in the mid to late 70s and then went to 40c a game in early 80s.
I definitely remember playing old EMs at Luna Park and Royal Easter Show from 1966 where they were sixpence a game. It took about 2 years to completely convert to  decimal but I think 5c worked as it was same size as sixpence. One reason I remember is because my mates were always asking for a spare zac for the pinnies. Late 60s and early 70s also had 10c machines.