PCB Rev 1 are working and usable but there is room for BOM cost optimization. Current sale price could be 89 EUR, with extensive BOM optimization it could be lowered - hopefully.
USB micro-B to USB mini change
FTDI USB connector is currently micro-B footprint (was actually mounted with micro-AB what is no go for real production). For some reason micro USB connectors cost much more than mini USB connector. As example chepest mini-USB connector at Mouser costs 0.145 EUR. Micro USB is currently in BOM with cost closer to 1 EUR!
This change requires moving the connector components to make more room, but it is still doable and fits the PCB edge area available.
The SOT23-6 packaged Operational Amplifier used for Analog input buffer for the Arduino Analog header inputs was chosen from our standard library, and is priced over 1 EUR. Footprint compatible part from Microchip costs 0.17 EUR only at Mouser. This is BOM change only no PCB change required.
Reset Diode Change
In the reset input we accidentially used almost first diode from our library it happened to be shottky diode in 0201 package, and not the cheapest one. This 0201 Diode is not so loved by SMD assembly operators as it is almost impossible to recognize the polarity marking as the Diode is bare die type, at the top the bare Si die is visible. This change required PCB change as well, PCB space is availabe no issues. Some BOM cost reduction will also come. Lowest cost diode at Mouser is about 0.032 EUR only. The 0201 Shottly Diode does cost much more.
VCC Switch Diode Change
There are 2 diodes in the schematic that are used to separate the power supplies, both list with 0.6 EUR in the BOM, quick search at Mouser shows suitable diodes priced 0.15 EUR.
USB Power Switch
TI power switch is listed with price over 1 EUR, quick search by Mouser shows SOT23-5 packaged USB Power switch pricing at about 0.35 EUR.
PCB Price and technology
PCB Rev 1 was made at prototype Factory so the PCB price for production can be lowered, but possible there may need to adjust the PCB technology and talk to the PCB fab about the pricing. Current PCB is 8 layer with small track and space rules and small vias. This will still most likely be the technology for production volumes as well.