Hello,
I've developed the module Newsletter Pro.
All the updates are free from the version 1 to the version 2.2.1 of the module.
In version 3.0 I've added many new features (newsletter pro front subscription, forward newsletter to a friend, etc...). That is the reason for the non free update between the version 2.0 and version 3.0.
I can offer the version 2.7.1 (that was never online) to all the customers that wants to update their older versions (they need to send me a message here https://addons.prestashop.com/en/write-to-developper?id_product=7484 . The customer needs to be logged in into their account, of which acquired the module).
Also, I can offer one time update to the version 3.2.5 to all the customers that purchase the module with 1 month before the version 3.2.5 release (between 11/17/2014 - 12/17/2014 ).
Regards,
Ovidiu