Extreme example is Tom Brady. Obviously, knowing what we know now, he would be the #1 pick in any draft class. But, taking him in the 1st, 2nd, 3rd, 4th, and to a less extent 5th rounds that year would have been bad value because you can get him later.
Another example: the market rate for an employee is $50,000 and you can hire him for that. It would be foolish to pay him $75,000, no matter how good you think he might be.