WhatsApp has a distinct advantage in the fact that it can rely on lock-in since the app itself is responsible for the connections that are made within it; Once

WhatsApp has a distinct advantage in the fact that it can rely on lock-in since the app itself is responsible for the connections that are made within it; Once the .99 price-tag comes along, you are faced with paying for it or losing your entire WhatsApp chat network/groups/etc. With OP's software, all of those connections are handled by FB, not his app. Therefore, if he were to charge something, people could simply opt for the next-best one that is free.