Who knows the GPL well?

[Greg Rundlett]

If you can find out who has a copy of the program (users/'customers'),
then you can ask them to kindly take advantage of their right to share
the source code.  Trying to charge a high price for GPL'd software is
doomed to fail in the long-run if the product is useful.  Eventually a
paid customer will invoke their priviledge to share the source code --
even when they might have paid a high monetary price for it.

1) You're a developer and are interested in contributing to the code,
but do not have incentive to pay for the original just to add your
contribution.  This benefits the 'customer' because they get the
contribution for free.
2) Your're a potential customer and are interested in evaluating the
quality of the source code in terms of how well it is defined, secure
and extensible (not just how it works from an end-user perspective). 
Any flaws or suggestions for improvement you would gladly share with
them.  This benefits the 'customer' because they get an audit and
possible contributions for free.
3) You're a support / integration / services company and would like to
competitively provide these services.  Breaking the monopoly of the
copyright holder is good for users/customers because they get more
breadth of choices for services, at more competitive rates.

All of these things actually benefit the copyright holder too.
1) Free employees
2) Free employees
3) Increased market penetration makes selling services possible/easier.