Why are we so productive with Rails?

Paul Butcher wrote:

http://about.82ask.com/2007/04/05/ruby-on-rails/

"On the back of this experience (and after a lot of internal debate!)
we decided to rewrite one of our existing PHP systems in Ruby on Rails
in June 2006. Including load testing, end-user trials etc, it took
three developers six weeks to entirely duplicate a 22,000 line PHP
system with approximately 5 man-years of work invested in it. The
final Rails system consisted of 6,000 lines of code."

Luv them rewrites. Could you have rewritten in PhP and achieved fewer
lines? Of course! But an order of magnitude fewer? That's the
definition of a Silver Bullet - an order of magnitude in one
rewrite...

DRY, soft typing, wall-to-wall unit tests, browser-safe JavaScript,
and instant Domain Specific Languages for everything - what more do we
need?