Budget planning, presumably. How much you are going to spend and on what, and what you need to charge for your products to break even or meet a profit goal.
I don't know how true it is today, but many a rollercoaster has been designed/planned in a spreadsheet. g-force and speed analysis, making sure there aren't any "blackout" points, etc. It allows you to iterate quickly and automatically appreciate the ramification of design decisions.