Donald Christainsen used to work in insurance, so he knows the price of priceless things like human lives. He knows the price of running over a young woman who isn't paying attention would be much less than the price of his daughter, who was killed by a driver who was texting. When he got the news of his daughter's death, his first thought had been what the driver's insurance would pay.
The way that Donald thinks about "the price of priceless things" suggests he'd like to think of the world like Natasha does, where it is easily quantified and not ruled by emotion. Indeed, his first thought after his daughter's death shows that he did, at that point, think that way.
Donald Christainsen pulls over and puts his head on the wheel. He touches his flask and thinks that people don't get over things like this. His daughter died two years ago, and the grief has taken everything: his marriage, his ability to feel, and his sobriety. He's not sure what the universe was trying to tell him when it took his daughter, but he learned that nobody can put a price on losing everything.
In the present, Donald seems to understand that a strictly rational way of thinking doesn't actually work in the face of overwhelming grief and emotion. This foreshadows Natasha's eventual shift to view the world more like Daniel does, and decide that emotion isn't that bad.