Most elements have a default unit price set for them in their properties. These prices are used in the project estimate.
If you have already created your design, you can edit the prices of inserted elements by selecting them in the drawing, then editing their properties. Alternatively you can generate and save a project estimate, then edit the pricing in the estimate’s associated editor, such as Excel or Notepad (depending on the report template used).
If you edit the price of any element in the catalog, the price change will affect all new insertions of the element.