> My understanding of the “duplication is cheaper than the wrong abstraction” idea, based on Sandi Metz’s post about it, is as follows. When a programmer refactors a piece of code to be less duplicative, that programmer replaces the duplicative code with a new, non-duplicative abstraction.

I think one of the main takeways from Sandi Metz's quote is that you should postpone creating the abstraction until after you have the duplicated code. Sometimes you will remove the duplication when you have just two implementations, sometimes you will want many more. Once you have the repeated code it's relatively easy to make the right abstraction.