This is a small example, so yeah, you're right, when the absolute times are so small. But say instead that it's a larger problem, and that #1 takes one day to

This is a small example, so yeah, you're right, when the absolute times are so small. But say instead that it's a larger problem, and that #1 takes one day to build, #2 takes a week, and the "preferred" solution (call it #3) takes two days. Then along comes your change request. It will take most of a day to rewrite #1 to do something never anticipated, but it can be slotted into #2 or #3 in about an hour. Now you've broke even between #1 and #3, and that's only the first change request. Any real system is going to get many more. These numbers are pulled out of thin air, of course, but they're pretty accurate according to my development experience.