Good versus bad design over time

The following diagram depicts the value of good design over time. As with most graphs, the x axis depicts the progression of time. The higher we go on the y axis, the more functionality and feature rich our application becomes. Below the design payoff line, applications with no design or poor design can quickly produce results.

However, there comes a point at which lack of design makes the application brittle, non-extensible, and difficult to understand:

The application that has been properly designed can be extended easily and becomes much more maintainable in the long run.

"Over 90% of software cost happens during maintenance phase."

- Fred Brooks, Mythical Man Month