I live in Brazil, so will post the project cost in Reais and also in Dollars (converted). It goes like this:

- PCB x5 R$65.78 (US$12.79) so US$2.56 each

- Raspberry Pi Pico W R$69.9 so US$13.60

- 0.96 OLED display R$29.90 so US$5.81

- 36x White 0805 LED R$17.28 so US$3.36 

So far the cost of the project (each unity) is US$25.33, a bit too high if you ask me. This is mainly due to the cost of the Pi Pico W in Brazil. For comparison the same product in the USA costs US$6 (https://www.pishop.us/product/raspberry-pi-pico-w/), so half the price.

I have not bought nor calculated the cost of the push button and 7-9 0805 SMD resistors, should be very low.