Otherwise, indeed, it's a basic evaluation error, as described as long ago as in the The Mythical Man-Month; it just seems that nowadays, the multiplier is not

Otherwise, indeed, it's a basic evaluation error, as described as long ago as in the The Mythical Man-Month; it just seems that nowadays, the multiplier is not 9, but even bigger. https://archive.org/details/mythicalmanmonth00fred https://archive.org/details/mythicalmanmonth00fred Figure 1.1, page 5 To go from a program to a programming system (interfaces, system integration), you need to multiply the effort by 3. To go from a program to a programming product (generalization, testing, documentation, maintainance), you need to multiply the effort by 3. So to get a programming system product, you need to multiply the effort from the program step, by 9. Nowadays, we need to compose indeed multipliers for distribution, reliability, availability, localization, targetting multiple UI platforms, etc. And the original multipliers are also probably too small, when you see the effort required just to integrate testing and CI on some projects.