The Central idea is that Egyptians burial ways are kind of like how we buried people. Another way that this is part of the central idea and show what kind of and how much currency that is needed for different types of burial methods and how they preserve and wrap the people.
The central idea supports the fact that family's with more money could have a complex type of mummification and better ways with more riches. They could preserve all of the different parts with all of the money. So pretty much they could do a lot more with more money.