Some interesting insights here. There might well be a lot more the developer could do to target his audience better. The pricing is not well explained and the model doesn't seem to make a lot of sense to me. One would think it would be easier to go after recurring revenue, perhaps even arrange a deal with instapaper to sell subscriptions on a percentage of revenue model. It seems a lot less awkward than "buy this account from someone else with recurring payments" then pay an upfront flat fee for an application.