Just fyi, I'm in Australia and can't view your software in the App Store as it's not available in my region. Not sure if the region locking is deliberate, but perhaps that's part of the reason that sales aren't taking off.
Just curious, what kind of software were you building with JavaFX? Was it for work or a side-project?
I've been interested in JavaFX for a while. As you mentioned, the technology actually seems quite good. But I barely ever see or hear about it being used in the wild which worries me.