I followed all the links that I could and didn't find any good information. I couldn't find build volume of the reference design.

I don't see how this will get traction if it really does cost $5,000.

B9Creator has been around for at least a year now and I think is a better choice if you want an open hardware design.

If you don't mind closed hardware, Form1 is $3,300. The material cost is a bit high though, even from third parties. I suspect the Spark might require expensive materials too.