yeah lately I've been thinking more and more about the benefits of a monthly subscription. People tend to be lazy, so even if they stop using a service, they'll continue paying for it, because they are too lazy to cancel. And $10/month just doesn't seem like that much money to most people, and gets lost in the credit card statement. So you are pretty much guaranteed your revenue, even if you completely stop selling.

Compare that to advertising models, where you need to work non-stop just to make sure you sell your ad-space to cover your next month's bills. Or one time fee models(sales/commission), where once again, you need to make sure you continue being on top of the food chain, to make those new sales every single month.

The good thing about monthly billing, is that you tend to keep those customers for a long ass time. So pretty much all you need is time to grow to profitability.

So you can have a very mediocre acquisition rate(lets say 5 new users per day), after a year of sales(@ $10/mo), you are already making $18,250 a month. And since you get paid month-in, month-out, you can spend a ton of money on advertising to continue growing. Because you have a fixed income.