I read somewhere a report that suggested that top software engineers tend to be up to 3 times more effective than average software engineers, and that 10x and the like is only really achievable in comparison to the worst engineers, and the worst engineers are often so bad that it's not sensible to compare with them. For a company, avoiding those guys is probably even more important than hiring the best - if your company has 10x engineers, your recruitment process is probably broken.

I have worked with some extremely productive software engineers. They tended to know the domain and codebase they were working in well, worked long hours and had either the enthusiasm, motivation or mental practice to maintain focus, and I believe those factors explained the majority of their advantage, which was large but not superhuman.

But like the author of this article, I've also seen a lot of situations where an apparently huge multiplier was best explained in some other way. For example, some apparently 10x engineers were only so because they were allowed to only work on interesting, relatively easy early stage work. The difficult, fiddly work of mopping up the awkward corners was left to other engineers, who were considered 'slow'.

Incidentally a lot of people will be a lot more productive if you let them work on only projects that interest them. I know some people who were considered 'problem' engineers because they spent most of their time doing stuff other than what they were asked to do, but they made a lot of interesting and useful stuff and with only a slight change in perspective or luck, they could have been considered 10x developers.

For maximum impact, having the wisdom and opportunity to work on the right thing is much more important than working 10x as hard.