Keep in mind that Americans' wages (especially minimum wage) have been lagging behind inflation since the 1940's, so disposable income is less available to the average American.

What do cultural difference between decades, or countries if you really want to go that far, have to do with dollar amounts? 

With movies there are the two comparisons, total box office and adjusted for inflation. The only one really missing that I could see being added is total tickets but the studios don't give those numbers most the time.

Comparing things monetarily over the span of years and only using the dollar amounts and not taking into account inflation, people today are making fortunes compare people back in the day, but with inflation things cost more as well. The dollar alone isn't a good unit of measure, like an inch, mile second or once. inches 80 years ago don't become miles today. Second don't become hours, but pennies turn to dollars. 

Now, you can look at movies and see why certain movies do well at various times, or what they did right to be popular, but that's discussing the reasons, not the results.

minimum wage in 1939, $0.25 adjusted for inflation that's $4.25 today. So in other aspects, compared to when the movie came out and shortly after people even with minimum wage are better off. While on hour of work for many people won't neccisarily cover a movie and a little more, there are many more people working and there are matiness and bargains people can find to make up the difference.

Also a movie like GWTW has kind of seen it all in terms of how the american wages are. considering it's release ans rereleases 1939, 1942, 1947, 1954, 1961, 1967, 1971, 1974, 1989 and 1998. So it ran a full spectrum of wages, had thousands of movies as competition yet people kept coming to see it.

That doesn't translate:

A movie ticket was $0.23 in 1939, and minimum wage was $0.28.

A movie ticket is $8.34 today, and minimum wage is $7.25.

That means that a ticket was less than minimum wage, and a ticket is now more.