[Drdrdrq]

There is a fourth control of course which comes into play when nothing else will give room: quality. You can take many shortcuts to deliver in time, full scope, with the resources available. But the result will be buggy and/or unmaintainable.

Surprising amount of companies choose this path, I guess most without realizing it.

[pas]

Quality is basically inherent in scope. Is testing the product in scope? Yes, then it will take up precious resources (time). Do you want to test it on every platform? Yes, even more time. (And of course the same goes for code review, writing unit tests, planning, writing and discussing a design document, etc.)