As I type this, I'm at the Recorded Sound room listening to the 3/20/70 episode of Sale of the Century!
I put in a request to listen to the four episodes listed on their website, but they hadn't been digitized and it would have taken 10 days to have access to them. The librarian did however have a digitized transcription disc with three Sale episodes and one Jeopardy episode, all from 1970.
By this point in the run, Madelyn Sanders had joined up as assistant and the Open Sale was still at the midpoint of the show instead of the Audience Sale. By this point, during the Instant Bargains Jack is more willing to haggle with the prices; he dropped the price of a fur coat from $13.95 to $5.
Incidentally, he hasn't gotten much better as host.
An example of the caliber of the questions:
"If you were abbreviating this writer's name, you might call him 'Ezra lb.'"
EDIT: I'm on the 7/23/70 episode of Sale now, and the Audience Sale is now in place. Three audience members are shown a prize (in this case, a $336 set of tires) and they each write down their guess of the sale price. Closest without going over wins it.
Before the winner is announced, each of the contestants select which audience player they think guessed correctly (or put up a 0 if they think all of them went over). Any player who guesses correct receives the sale price--in this case, $17.95--added to their score as a bonus.