Nobody wants 10x developers these days. All companies are looking for 1/x developers because then they can brag about their head count to get acquired or to raise more money from investors or banks.
We all know that start-ups work because they are small and focus on problem solving, not dealing with bureaucracy and administrative inefficiencies.
Look at the whatsapp acquisition. It was touted so much because the company had only 50 engineers.
High revenue per headcount is a good indicator of successful execution, good hiring practices and organizational structure, and a solid culture.
If you can achieve the same results with 5 people that a company needs 20 people for, you'll obviously be the more profitable and desirable company for a VC to invest in.
For example, it makes little sense for a company to use a different web framework every year. It makes sense for individual developers to accumulate a large list for their resume.
Likewise, it makes not sense for a company to optimize for a large headcount. It does make sense for an individual manager because leading 100 people looks better than 20 on his resume.