Repay what? The people of modern Egypt have no connection or inheritance claim to the ancient artifacts, other than their having been created in a similar place where the modern Egyptians are currently living. They don't even share a remotely similar culture. The same is true of many other places that had their artifacts collected, in that the people have no legal claim to the artifacts other than their having existed in a place in time nor do they often have any shared culture with the people who created the artifacts.