Quote:
I'm sure there were 5 million readers in America in early 1950.

Total readers? Sure; way more I bet. But not of one title. No comic truly sold 5 million a month, ever. X-Men #1 sold 8 million variants. The most successful was probably Walt Disney in the 50s, with 2.8 million. (If you count Mad, that was maybe 1-2 million). Superman at its peak was 1.6 million, cira 1946.