KmH, Bitter and others have raised excellent points. As someone who's career is in Business (and IT) management, let me re-iterate some fundamental truths:
1. You cannot support a business with cash infusions. You can to get started, that's how most businesses actually get off the ground, but long-term it's just not sustainable (ask the 100,000+ IT/Business folks who suddenly found themselves out of a job when the dot.com bubble burst... I'm one of them).
2. There's a danger in keeping yourself at the bottom of the price point for the market you are in. You may get some business, but by undercutting everyone else (i.e. the "pro's") you will never make a profit, you'll get a reputation as a budget service. When a business enters a market space, there's two main barriers: technical ability to deliver a product consumers want, and the ability to deliver that product at a price point the market will bear. Photography has a small barrier to entry these days as far as equipment goes (so they can charge less to cover equipment costs), but the technical ability to deliver is what will hit you the hardest. Never mind the business savvy to actually run a for-profit business.
3. As other's have said, it's way cheaper (by a factor of 10 or more) to retain customers than getting new customers. Advertising is expensive, both in materials and the time required.
I don't have a photography business, I have a hobby. Since it's a hobby, it's supported 100% by my actual career. I sell prints just to make teeny tiny dents in the costs to continue my hobby, not to make a profit.
I'm glad you found customers which are happy with your work. More power to you and I hope you continue to get paying customers. But don't be surprised if doing what you are doing never leads you beyond being "that part-time photog who does everything super cheap for so-so results".