There is tremendous growth potential for Shapeways, but I have to agree with the stated opinions that you aren't going to get significant income just for showing up and making models. This is a very young industry, so the most reward is going to go to those who create new applications and innovative solutions that leverage the strengths of the technology. Just editing the label on a very expensive version of a common product is rarely going to create an object that people really desire. I would say that designing for 3D printing is a little like the restaurant business. There is a huge demand for food, at both the high-end and low-end, but the reality is that nine out of ten restaurants fail. There are many things that need to be perfectly set in place, and if anything at all is missing or done badly, the business will not work. Even if the exectution is brilliant, marketing and promotion are different skillsets, totally unrelated to the quality of the product.
Twopounder- what you are describing has a name. It's called Rapid Tooling, rather than rapid prototyping. It is a very mature industry technique that was developed along with the prototyping application. Almost every major manufacturer is using it, but there is growth opportunity there too, as the technologies become more accessible to designers and small manufacturers. I have been offering services in rapid-tooling for short-run manufacturing in the form of mold tool generation, usually from designs that I create on commision, but I do offer it as a service to anyone wishing to create molds. I haven't focused much on this, because it is the role of a design-engineer more than a designer, but I'm happy to do a little business and enable others to make their product a reality.
So, a potential development pipeline would be to create your design, print and refine the prototype, have a mold tool created and printed, then either outsource the manufacturing or do it yourself. Notice that this reduces the per-part cost, but increases the lead-time and initial expense, and doesn't do anything at all for marketing and promotion, so an integrated digital production pipeline is an incredible way of starting off a product. From here on, the burden is on the designer to make it happen, intially. If you develop something suitable for mass production, then you can pursue it with confidence, having proven it's value at the higher pice-point of individually manufactured items,