Well, it's the challenge of finding one person who can talk sales/marketing language to executives as easily as they can talk with their technical teams all while being highly organized and capable of managing a team.
They don't need to be masters at any one of those things (aside from organization and management), but they need to be well above average at all of them, which is rare nexus of talents to find.
Also, experience and skills like that are usually earned through entry-level work in other fields. Most of the good PMs I work with came up through other career paths (like non-profits, academia, print or tv production, paralegals, etc.) that are typically not so well compensated. They make lateral moves into product management for financial reasons, and they top out quickly. The highest paid PMs I know were mostly just former engineers themselves.
They don't need to be masters at any one of those things (aside from organization and management), but they need to be well above average at all of them, which is rare nexus of talents to find.
Also, experience and skills like that are usually earned through entry-level work in other fields. Most of the good PMs I work with came up through other career paths (like non-profits, academia, print or tv production, paralegals, etc.) that are typically not so well compensated. They make lateral moves into product management for financial reasons, and they top out quickly. The highest paid PMs I know were mostly just former engineers themselves.