ClamXAV has been donationware since it's beginnings. But with version 3, it will be ~30 bucks a year. If you have a registered copy, you can upgrade for a life-time rate of ~15 bucks. Other discounts are available for new purchasers. Version 2 will no longer receive virus definition updates after Oct. 2018.
I can't argue with ~$1.25/month! Even twice that is reasonable, I think.
The dev has obviously hired programmers and poured his heart into continuing to provide a very stable and useful Mac app. I recommend upgrading to the new version while these discounts are available!
Edit:Changed the topic title. Not sure how it became "$1.25". 
I can only assume I accidentally entered that as the "Subject". 
