A meaningful anecdote from Overheard in the Office:

HR #1: Why would anyone agree to take on more responsibility if we're not going to pay them more?
HR #2: We're giving them more projects to work on that will be more advanced than what they're working on right now. I think people look for a challenge and they will be willing to take on more responsibility if it promises to be rewarding. Besides, most of them are in their twenties and need to start somewhere. So you see, we really are paying them more...in experience.
HR #1: Who is ever going to fall for that?

I did... for the last 2 years. Watch out, kids.