> This could just be because I'm a mediocre developer (1X) but:
If you're mediocre as in average, that makes you 4x, not 1x. The 10x developer is 10 times better than the worst performer who is still employed, or 2.5x the median.
I only point this out because lots of people get it wrong and end up unfairly underestimating their own competence.