Hacker News Reader

The rest is passive junk that's probably about 25¢.

That's more than $5, but this is what 120 seconds of searching on AliExpress turned up.

Software is where a lot of the value comes from. I assume it's using a clever hack like http://dmitry.gr/index.php?r=05.Projects&proj=11.%20Bluetoot...

well: arduino [1]: 1.38$ nrf [2]: 0.55$ oled [3]: 2.33$ ------------------ total: 4.26$

like you said the passive components are pretty cheap, and you stay under 5$.