I've met someone who I'd call 10×. I've worked with him. He once wrote a usable spreadsheet, with a fine set of formulae and an entirely plausible UI, in an evening and a night.

His code had major issues, but that's not to say that he couldn't write software. He could, in a manner completely different from me. Amazingly well, yet frustrating.

Above a certain level, one developer isn't universally better than another. It's not linear any more.

He's a CS professor now.