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 performance out of frameworks based on poor interpreter implementations.
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.
As I see it, speed is the last big advantage Java has over Python (and I do realize that a dynamically typed language makes achieving efficiency harder).
Apparently PyPy has some financial support from Google (http://en.wikipedia.org/wiki/Pypy#Project_status), but it really seems like basically any company that uses Python would gain so much from robust JIT compilation in the interpreter that I'm surprised there's not a more concerted effort to make it happen.