Building Arduino Nano from components At this stage, my finalized design includes Arduino Nano 3.0, a breakout board and a few electrical components on a breadboard. 

Will there be an appreciable cost savings from not buying a ready-made Arduino? The Arduino Nano clone being used costs $17.20. 

And is it a good idea if everything is soldered on to a custom fabricated PCB board, including the components of Arduino Nano 3.0? The PCB board will cost around $10 at the quantities I'm starting with.
You can probably do a lot better than $17 but not much better than $8:

http://www.ebay.com/itm/Mini-USB-Nano-V3-0-ATmega328P-5V-Micro-controller-Board-For-Arduino-compatible-/130977189883?pt=LH_DefaultDomain_0&amp;hash=item1e7ed94ffb

If you don't need USB, you can use a Pro Mini and they go for about $4 and that's really hard to beat.