No effort

My Facebook App (At The Moment ...) now has 72 users. It's been growing in drips and drabs without any effort on my part. I am basically using Appsaholic to advertise other apps on my app, then when I've arned a few dollars, spending it advertising my app. It's a slow process but it is no effort and it's growing. Makes me wonder what would happen if I was to sink $100 into advertising it, but I just don't think it's worth the expense, as the revenue per user is very, very low. I think to earn an average income an app would need a very large amount of users who use the app every day. ATM only gets used by a few people per day even though it has over 70 subscribed.