didn't work for me

They basically did what you were saying... as I have read here, anyone who has purchased an extension in the last 30 days can have that money applied towards the subscription... I am sure they would be willing to carry that on... where someone could try out dataAssist, for example, decide they love WebAssist stuff and then could call sales and instead have their purchase applied to the subscription instead. While I don't want to speak for WebAssist, this appears what they are doing right now.
Best regards,
Brian

I guess not all people can receive that deal, here is the response I received:
Thank you for your inquiry. Unfortunately, I cannot apply the $79.99 you spent on 8/25 to the activation fee, however because you had made that purchase with us, you are being offered the upgrade discount activation fee of $49.99 (retails for $79.99). Please click on the following link to enroll for the $49.99 price via your Upgrade Center: