There are two kinds of developers:
1. Those who are good developers 2. Those who can't write any real code (cargo cult or cut&paste developers, e.g. the 25% who I didn't hire over the years because they were not able to FizzBuzz)(25%-50% of the market)
The 10x comes from comparing (1) and (2) - although dividing anything by 0 is larger than 10x.