I think another big part of deciding to use DRY is the complexity of what you're repeating. Copying and pasting lots of business rules means having to make comp

I think another big part of deciding to use DRY is the complexity of what you're repeating. Copying and pasting lots of business rules means having to make complex edits whenever that logic needs to change. Having simple rules and a small amount of surface area for data reduces the initial need to have DRY code, and it's easier to take the initial risk of using duplicate code. At least in my experience, it's easier to start with duplicates of simple logic/data, and use DRY for more complex logic/data. The difficult areas are still those where the logic and/or data fall between simple and complex, or are expected to change often, but unknown whether they will change together or diverge quickly.