This isn't a game of inflation, it is a game of ticket sales.
A ticket for a ticket, 1 for 1.
Gone with the Wind made more money overseas then it did domestically. Adjusted it is around $1.7 billion domestically, and some where between $1.7 billion and $2 billion overseas. That it is why its worldwide total adjusted between $3.4 billion and $3.7 billion.
http://www.boxofficemojo.com/movies/?id=gonewiththewind.htm
I wasn't alive in the 60s, but The Graduate was beloved and had a rather large impact on culture.
The Force Awakens is showing exactly what a film with real impact can do domestically. It is going to do OT money adjusted, and might only be behind Star Wars when it is all said and done. So we can't say it is impossible to do that kind of money now, as TFA is showing that you most certainly can. Avatar, while I may dislike it, also showed this. Same with that movie about a boat.