How much did McDonald's use to cost in 1972?

After searching through a number website, this seem the most reliable.

"[1972] We find several articles about a scandal concering the McDonald's food prices and the Federal Price Commission, no simple hamburger prices quote in tje New York Times. Sample here: "Quarter pounder priced at 55 cents." --"McDonald's Told to Reduce Prices,"New York Times, June 3, 1972 (p.21)"

Source: http://www.foodtimeline.org/foodfaq5.html#mcdonalds

I hope this helps