Correct, the price of a NY to SFO ticket in the 1960s was $363 (today it's still $320). But keep in mind that in 1960, the median home cost $13,000; a new car was $2500; and gas was $0.25/gallon. The new prices are approximately 13x higher (thanks inflation). Which means that relative to other goods, the current price of a ticket would be about $5000-6000!
If the mandated lowest price for a round trip cross country flight was $5500, and airlines could only compete via what services they offered, how much service do you thing they would offer to get that business and most of the $5,000 premium? It turned out that most people didn't place anywhere near $5,000 on those services (it's only people who weren't paying anywhere near that price to fly (like travel agents and family of airline employees) who miss the old days.