MiniRock,

I don't think you're grasping the concept of inflation adjustment. Movies with sound in them were cutting edge technology at one point, and the introduction of sound playback equipment probably boosted the ticket prices for movies back then. $1 in the 1930s was worth a heck of a lot more than it is today. That's why adjusting for inflation is important.

It is because a ticket cost about 20 cents in the 1930s that it is important to adjust that figure upward if you're trying to make any sort of meaningful comparison to movies being released decades later. Not as many people have to see a movie today for it to gross more than a movie from the the 30s.