However, I cannot state enough that the price of this small component was simply not where the costs accumulated on this project. We geeks have a nasty tendency to over-optimize things that just don't matter in the big picture. You totally nailed it when you mentioned that this device is a packaged (and QA'd) product. The fact that it just slips right onto a Pi's GPIO pins without requiring any further modification is what makes this such a win. If you have to do anything to [70 units of] a component to make it work, you're blowing up any miniscule price arbitrage anyhow.