We have big enterprise projects they normally involve copying data from a source database to a destination database and then setting up a number of additional applications that sync this data etc.
The last project contained 250,000 items (rows of data). The next project will only contain 4,000 items. Project managers / business people believe the project should be 1/10 the time to complete because its only a fraction of the size of the last project.
What is a good analogy I can use to explain that writing code to transfer data from one system to another takes the same amount regardless of the number items - writing it for 1 item or for 100,000,000 will take roughly the same amount of time from a programming point of view.