The key thing to note is how much of the manufacturing process is completely automated. Due to the huge volumes of the rPi it is cost-effective to automate almo

The key thing to note is how much of the manufacturing process is completely automated. Due to the huge volumes of the rPi it is cost-effective to automate almost the entire process. On the other hand, for products expected to sell only in the thousands or tens of thousands it turns out human labor is cheaper. In the rPi's case, notice that it got soldered twice. Once for SMD (surface mount device) parts and once for the larger through-hole parts. In general, if there aren't going to be huge volumes humans will hand solder the through hole parts since a separate wave-soldering machine is needed to do this automatically. As another example take a look at the custom testing jig they shelled out for. That is easily thousands of dollars if not even north of 10K. Again in small volumes it would make more sense for humans to spend the extra effort setting up the board for testing.