[nostrademons]

It does explain the model - each feature is given a certain number of developer days that are billed out at $450/day. It's all broken down if you click "show calculations".

I personally think their model is pretty shitty, because if you build an app as a checklist of features you'll end up with something users won't want to use, and if you polish all the rough edges and make sure everything integrates well together, you will spend a lot more time on integrations than on implementing the features. (My rule of thumb - across many projects - is that when a project is feature-complete, it is usually between 40-50% shippable. When it ships, it is about 50% "done", where "done" means that all the initial development tasks required to make it stable and useful to users are complete. When it's "done", it's consumed roughly 10% of the calendar time and 50% of the developer time that will ultimately be invested in the project.)

But you can at least judge the model they're using for yourself.