The problem with OSH is that the people who give a shit about it being open are just going to build it themselves and not bother buying anything from you.
In some cases this is true. However, there are other factors that come into it.
I own a couple of arduinos. Even though I have the skills to build one and I suppose it would be a bit of fun to do so, I chose to buy them. Why? For me, the biggest limitation is time. I have so many crazy ideas, and there is so little time! I bought each of my arduinos for a specific project. I prefer to spend my limited time on the projects themselves rather than building an arduino. I can buy the parts for an arduino for around $15, or I could buy one fully assembled for around $30. It'd probably take me a 3-4 hours to build and test an arduino and I would save $15. I don't know about you but my time is worth more than $3.75/hr.
Also, as these projects evolve they will almost certainly become more and more complex. Small scale manufacturing may not be able to match the efficiency of full scale manufacturing.
Lawrence Radiation Laboratory keeps all its data in an old gray trunk.