Prices on the market not only reflect the player's attributes, but also how much of an asset he can be to your team.
I mean, if a 27 years old is a beast, the only value he's going to give your team is going to be his on-court production.
However, if he's not that good, but is 20 years old, he could be a much more valuable asset to your team because you can make money out of him.
"Air is beautiful, yet you cannot see it. It's soft, yet you cannot touch it. Air is a little like my brain." - Jean-Claude Van Damme