Blind joined Ajax for a club record fee worth €20.5m.
"In principle, we paid far too much for Daley, but Daley himself knows that too, because I told him that," said Overmars.
The sports director admitted they paid over the odds as time was against them.
"We really wanted to have everything in order, because it was important to start well. That is why we have gone further."
Overmars says the deal was done with the view to Blind helping Matthijs de Ligt.
"It was also important for Matthijs, because I knew that Matthijs would like to play together with Daley for the Oranje. I thought: now you have to continue here."