How much did it cost to apply for a cb license back in the 70s?

In the early 1970s, a citizens' band (CB) radio license cost around $20, but the cost went down to around $4 by the end of the 1970s.

One of the uses of CB radio in the early 1970s was for truckers to communicate with each other about where gas was available during the oil crisis caused by an oil embargo placed on the United States by Arab oil exporting countries.  (The embargo was because the US supported Israel in a war vs. Arab states.)