I've already supported the developer by buying the previous versions on iPhone, iPad and Mac, now presumably I'll have to buy them all over again for a relatively minor upgrade. I love Reeder, but I don't think I'll be continually buying every version.
As a consumer, you are entitled to feel that you are not getting your money's worth. But RSS has become more of a niche service, especially after Google Reader shutdown. So the developer is facing much smaller market for Reeder 2 for Mac.