re:
sample - Looking at CyberCoders job postings for New York right now it only shows 252 job posts in total so the sample is very small.
And you can slice and dice this kind of data in so many ways you can end of with many different types of results from it :)
Searching on CyberCoders for PHP, Python, Ruby & Perl at moment (in NY) returns these numbers of job posts...
PHP 48
Python 33
Ruby 27
Perl 13
However if we then break this down into clearly defined posts for a PHP developer, Python developer, etc we get...
PHP 9
Python 8
Ruby 9 (3 Ruby, 6 RoR)
Perl 1
And the average salary range given for these developer posts are...
PHP $80k - $121k
Python $93k - $128k
Ruby $83k - $128k
Perl $80k - $110k
As with quoted figures everywhere please take these with a large pinch of salt :)