From the Lawrence Daily Journal-World for June 23, 1972:

A report from Washington, D.C., revealed that food prices had dropped over the last month (except in the category of fresh fruits and vegetables) but clothing and transportation costs had increased, leading to a net increase in the cost of living. The Bureau of Labor Statistics also reported that the average wages of 50 million “rank and file” workers had risen about two cents per hour. Lawrence bargain-hungers could find relief at Burger Chef, 9th and Iowa, which proclaimed that “You Can’t Cook Hamburgers at Home for These Prices!” On “Family Night,” Wednesdays from 5 to 9 p.m., hamburgers sold for 15 cents, cheeseburgers for 20, double cheeseburgers or the “Big Chef” for 39, and for those with really big 1970s appetites, the “Super Chef” was available for 55 cents.