Problem
You can't edit the unit price of a material in an estimate as the Unit Price field is grayed out. This happens if the material isn't marked as chargeable or if you don't have the appropriate material permissions enabled.
Solution
Make material chargeable
Make sure you have the Edit material price and Edit Material Charge permissions enabled for your profile. If you can't view or edit permissions, contact your administrator.
Find the material you want to edit in the estimate.
Find the Chargeable column for the material. If it's gray, the material is set as non-chargeable.
Click the Chargeable toggle to make the material chargeable.

After following these steps, you can now edit the unit price of a material in your estimate.