During a design meeting of a new project the issue of performance is raised.
This is the theoretical (worst-case scenario) performance requirement:
As existing frameworks and 3rd party tools don't match these requirements, new frameworks will be developed.
After spending many men-months on developing new frameworks (even before the development of the application itself) this is the application's performance:
Eventually the application is shipped, and customers are satisfied with the performance.
However, this is the average case performance requirement:
(NIH = "not invented here", a common syndrome in the software industry leading to spending resources to create new tools instead of using existing ones)