It highly depends on how you measure value. If you measure value in terms of what they bring to the overall organization, people from top 10 schools are very likely overvalued. If you measure what value they bring to the team, top 10 schools are probably correctly valued. The difference is that the manager of the team hiring from Harvard can speak to people in more senior roles about how great their team is and how they have the best talent.

At the end of the day, value is driven by how much political leverage a hire can give a manager, not by how much value they add to the org.