A productivity difference of 10X-20X is well documented. I've seen it several times. Note that's average productivity over a year, not consistently every day. Here's an example:
I've seen more than one instance in which a average, "competent" developer will spend 10 days writing a module to add feature X to some software, to solve business need Y. The expert/guru/rockstar will spend ten minutes changing a setting to solve the same problem.
So the average person spent ten working days, the expert spent ten minutes in this one case. The expert could then be only equally as productive for the rest of day and they will have accomplished in one day more than the first person accomplished in ten days. I very often solve business needs by _removing_ code, removing a restriction or problem. You can imagine that removing a blocking problem can easily be ten times as productive as the typical approach of solving new problems or handling new tasks by building new systems. Simply asking "why can't we use the existing system for this new task?", then tweaking the existing system to handle the new requirement, can be hugely more productive than starting out with the idea that new tasks require new systems to be built.