Earlier quoted context omitted.
Raw execution speed does matter, but like any incremental cost, is often ignored. Off-the-cuff benchmarks I ran on our Scala-based webapp on a four-core desktop system demonstrated 5,000 req/sec @ 2ms/request after the JIT warmed up. 5,000+ requests/second -- scaling up with available CPUs -- means not having to worry about performance, complicated caching, and the slew of other things that developers do to eek perfo…
It's not really an incremental cost but rather a constant overhead. The idea is that if you're worried about performance and scaling then you'll have to find a way to distribute your load over multiple physical machines anyways. At that point it doesn't matter so much anymore whether one of your nodes handles 5000 reqs/sec or 2500 reqs/sec. Hardware is cheap.
In reality, neither hardware or development are cheap, and performance does not inherently necessitate more costly development. The mantra and the dichotomy are false.