In reality this is a qualitative metric. If you can produce value as quick as our CTO Shevek then we will have no issue paying you at the top of the range.
As a bootstrapped company (9 employees in 6 countries, no two of us have the same nationality) - we pay a reasonable base and pay a significant year end bonus that is influenced by your work during the year, our profitability and where you live.
No doubt this is not a satisfying answer, but as a small company we have great flexibility to structure packages to meet each team member's requirements.