The reason a lot of teachers impose a, "cost," is often to teach responsibility and to affirm those who got their act together and turned it in on time. The concern with this approach, however, is that we're saying that the cost comes in the form of falsifying the report of student learning, which is not helpful or ethical, and it definitely doesn't teach personal responsibility or time management. The research is quite clear that punitive grades and falsifying learning reports by conflating compliance or timeliness with learning does not teach build maturity the way many think it does. It would be worth looking at those other elements for teaching these virtues and work habits, such as student agency, executive function, fostering independence, self-monitoring learning progress, meaning-making, and more. For now, though, let's make the "cost" of being late sacrificing other, preferred activities for sake of needing to finish work in a timely manner, requiring student reflection on decisions made that did not yield mature results, building executive function skills, helping to remove biases and obstacles that keep students from focusing on learning, reporting on personal work habits separately from academic proficiency in content, and similar. They do a much better job of student personal growth and accountability.