Ouh well....They just want to hook you to download the plugin and deceive us that it has been downloaded or rather bought so many times after they get many downloads from free as it shows on the plugin page they change it to paid and you will think those people who downloaded the plugin bought it but in reality it was offered free so that they can hook other users to buy at your "free plugin download" lie
If I was to offer a free plugin that I was going to start charging for I would most definitelymake the community aware. I dont change my prices however unless they go lower or go on sale. :)