Contractor Markups on materials

[Svetlana G.]

We are working on a project and I reviewed the pricing/ invoice provided by our contractor. He broke down everything by labor and materials. Specifically, my question is about the pricing for one item. I looked up the system he is using for reinstalling a closet doors. He quoted materials only as $60 per door + a separate fee for labor, the exact track system (I double checked the item number on the box) at home depot is $12.98, he needed some additional items, wood and small screws, which add up to $10 at most!!!  is this a common mark up???  I understand that they charge for their time and effort to go and pick up things from the store....but still. 

I sent them a note asking to double check their receipts and update the estimate provided accordingly. What is the right approach here?

Thanks in advance!