In 1967 The Monkees sold 35 million records, outselling The Beatles and The Rolling Stones combined.
Actually, Michael Nesmith admitted (boasted?) in a recent podcast interview (Gilbert Gottfried's Amazing Collossal Podcast) that he was the source of that factoid, and completely made that number up.
He was being interviewed by the NYT, and told the interviewer ahead of time that he was going to lie to him. During the interview, he convinced the NYT interviewer that the Monkees were still doing great, and in fact worldwide sold 35 million records last year (1967).
Sure enough, when he picked up the paper with the interview in it, the NYT had reported his lie as fact. And of course the factoid was picked up by Rolling Stones, and pretty much everyone else, and is believed by most to this day.