Integrate with payment method, charge per use or monthly

Please see this comment for details:
http://drupal.org/node/663332#comment-2607706

We'd like to be able to use phplist for sending emails instead of commercial services but we need a way to cover the cost of supporting and operating the service.

How can we tie the use of this module to a payment gateway (paypal / ubercart)?
Can these payment methods be added to the email marketing framework as alternatives to commercial services?

Example Options:

Starter - phplist (free for under 500)
Simple - phplist ($ for over 500, billed via pp/ubercart)
Advanced - Campaign Monitor via EMF ($ per send + per email, billed via CM)

Detailed user interface specs and overall project spec provided as needed.
(willing to sponsor this development, use contact link or leave comment here)