Not clear how performance & scalability is a trade-off

Created by: Lou-E-303

The section on performance & scalability seems to suggest that these two factors are a trade-off between each other (Keep in mind that everything is a trade-off., etc.). Even the language of 'performance vs scalability' seems to suggest that having one comes at the cost of another.

But then, the section explicitly states that as a service scales, the performance increases if it is scalable.

It is therefore unclear to me how this is a trade-off, and unless I've misunderstood something I don't believe this really belongs in the 'high-level trade off' section with, say, CAP Theorem.