Pretty sure the comment you're replying to is talking about development time, not compile time. They're claiming it took months longer to develop a similar app in C, not that it took longer to compile. Even if compile times are negligible now for the reasons you state, they still have a point about it taking longer to develop an equivalent app.
No, I believe it means the programmer gets automatically paid when milestones are marked as done. They are referring to the 3.5k being paid for the job. Any revenue the app gets has nothing to do with them.