When you start to create that payment module, you can predict its complexity. You have an experience of creating software, including payment modules. You can sa

When you start to create that payment module, you can predict its complexity. You have an experience of creating software, including payment modules. You can say that the module will be 1500 SLoC in size. This is what COCOMO prediction mechanism is based on, the SLoC metric. I'm saying that this metric is wrong. And almost everybody agrees with this. But HoC metric is perfectly suitable for such a prediction. You can say that this payment module will take 50000 HoC of my effort. And then you track performance based on this number. And you can estimate costs. Just like COCOMO, but using HoC.