That seems thoroughly unfair. For one thing, Reeder supports the iOS 8 share sheet, which should really render the other options obsolete in the long run. You can just use the share sheet and share to any email address you want.
Also, what world do you live in where you feel that a one-time $5 purchase entitles you to a lifetime of development and support from any developer? It takes constant work on the developer's part, not only adding new features but keeping up to date on new iOS versions and, changes to APIs, bug fixes, etc. Your old version of Reeder isn't disabled when a new version comes out, but at some point you have to pay if you want the developer to have the ability to continue to support their software. This is just reality of anyone who wants to make a living developing software for mobile devices. Desktop applications have been charging for significant upgrades since forever. Apple doesn't allow for upgrade pricing, but the average price of an iOS app is so tiny compared your average Mac or Windows app that it's not at all unreasonable to just pay "full price" every once in a while. It's about the cost of a medium latte at Starbucks…