OmniPlan for Estimating
 

Lately I've been using OmniPlan to estimate projects in proposals, but it could work a little better for this.

It would be nice if I could control the granularity of costs it lists (for example, only for top-level tasks), and if I could have it show an overall total at the bottom.

You can get the total cost in the bottom of the window. At the bottom left corner of the OmniPlan window, there's + and - buttons and a gear button and then some text. The text probably is the project's start and end dates right now. You can click on this text a few times to cycle through some other properties of the project, including the cost.

You could artificially control the granularity through an additional custom data column and an AppleScript to keep it updated, but this may be more trouble than it's worth.

Besides a grand total at the bottom, you can arrange your tasks in hierarchical groups. OmniPlan will roll up the duration, progress, and cost.