Usually have to be either very attractive (Demi Moore) or significantly better off to get a younger male. The older men only have to be rich or famous or of perceived "high status" (Hugh Hefner).

I once knew an older man who worked for Frederico Fellini. He won an Oscar for his work on one of Fellini's films. I was 20, he was around 70. I was not attracted to him, however, there were some 20 something females who were attracted to this guy once they found out who he was. They would not have looked at him twice had he just been any old guy walking down the street - but once his status was revealed they were practically dry humping him at dinner.

I still wasn't interested. However he took a great interest in me, and I'm SURE I wasn't as hot looking as some of these bimbos who were after him.

Moral - people want what they (think they) can't get.