We're thinking not of financial matters here, but "matter matters". Specifically, the issue of printing overhangs. A 3D printer deposits material layer by layer - and there's kind of a major issue if there is nothing underneath the layer. Print media falls by gravity and your object doesn't quite look like it should. Bad.
The solution to the problem is to somehow provide temporary support structures that hold the overhanging material in place while the rest of the object appears. If designed correctly, the overhang will be connected to the rest of the object and all is well after the temporary supports are removed.
But what are these supports, and where do they come from? We read an interesting discussion on the RepRap forums, whose readers pondered the question of overhangs exceeding 45 degrees. A variety of solutions were proposed, demonstrating that this issue has not yet been solved satisfactorily. One point we agree with, however, was the idea that the object designer should not be responsible for determining the support structure. Designers should create beauty or utility; supports are work best done by software.