The only problem with your math is that you have residual value in the machines. I'm definitely not suggesting you are getting rich (you aren't). You are growing your collection for much less than most people though.
Quoted from Thermionic:but is it time for Stern, JJP, et al. to consider outsourcing at least some of the build process to cheaper labor/regulatory markets?
I would guess that the biggest cost of the machines isn't the actual building of them. I would think its more of the modeling, design, prototyping etc.
You would think they could make a lot more money if they started selling parts themselves though (Stern anyways, not the boutiques). They are already ordering large quantities, why not make even more money selling those parts, and being able to get bigger discounts.