The seventies where the pinnacle of classic rock music . speaking about costs of some of the gigs in those days , I remember AC DC playing at the south Curl Curl community hall back in 1975 this is in Sydney Australia and all I paid was $1.00 there were probably only about 100 people that attended but in those days you could jump on the stage and sing with them.
And INXS used to play every Thursday at the Mosman hotel in Sydney this would be in the late 70's early 80's and they were free of charge
The music of those days have made am impact on the industry today and the songs are still popular even amongst the youth of today