I didn't really think about the BOM cost of my programmable decade resistor until I was asked. Then I also wanted to know. It is fairly difficult to put a number to what I paid, since I had a lot of components left from other projects that I could use. This includes not only cheap chip resistors and MLCCs, but also connectors, the microcontrollers etc.

Normally, I order my parts from mouser and digikey. For some of the industry-standard components, connectors etc. I also use local distributors (cheaper!). This is why I'll only give a very rough estimate for the per unit costs including taxes (and not including any shipping costs). For some of the parts like the PCBs there is a minimum order quantity that will increase the cost in most DIY scenarios.

Mechanical parts

Mainboard

UI Board

Power supply board

Conclusion

According to this calculation the total cost of the unit would be about 369 €. Quite a lot, actually. This doesn’t necessarily reflect what I paid for it though. One example: I bought 5 NE-18 type switches on ebay for about 2 € each. These are not necessarily the same as the ones provided by mouser, but both variants could be used.