This is the path that financial analysis usually follows. We start with a simple back off the envelop, then complicate things in Excel. In presentation design, the last step is crucial: bringing down that Excel model back to a simple calculation.

And that simple calculation is likely to be completely different from the one you started off with. Building the complex model has taught you how your business really works financially. And only when you understand that, can you go back to simple.

Most of the times, presentations stop in the middle. They throw the data output form the complex model at the audience. That is a sign that you do not understand it yet, and if you don't get it, the audience will not get it for sure.