1 AdaFruit ItsyBitsy (32-bit ARM®, SAMD51 Cortex®-M4F MCU)*   $14.95
2 MICROCHIP - 25LC512-I/P - 512K SPI™ Bus Serial EEPROM DIP8    3.30
1 SSD1306 I2C LED display 128x32 pixels.                        2.23
1 micro USB to USB cable 100cm                                  0.69
1 Custom PCB                                                    0.48
1 Rotary Encoder                                                0.46
PCB Shipping to USA from China                                  0.72
1 plastic knob for rotary encoder                               0.11
2 IC DIP Sockets, 8 pins each                                   0.10
Solder                                                         ~0.10
1 RGB LED diffused 5mm                                          0.03
3 220ohm resistors                                              0.01
2 4.7kohm resistors                                             0.01
                                                          ----------
Total Parts                                                   $23.19
                                                          ==========
Not included: shipping, packaging, and assembly costs.