I don't think that a single developer can be thought of as 10 times as productive. But a good developer absolutely can have a tenth of the "collateral damage" a

I don't think that a single developer can be thought of as 10 times as productive. But a good developer absolutely can have a tenth of the "collateral damage" after releasing a product with less need for support, fixes, and refactoring. If I think of it as team dynamics, I can see a single developer making that much of a difference. On his own (s)he is not that much better than your average developer, but in a team (s)he can lift the team with his/her experience and really make them significantly better. 10 times better is probably a stretch, but measurably better at least.