For the light-attached end, it is down to $10 with this like the HUZZAH ESP8266 Breakout. At that price, the LED nearly becomes the most expensive part of the setup (assuming you want anything more than a single color and/or light).

What I love about the ESP8266 + NeoPixel style setup is that it gives you control over the form factor. For example: https://www.instructables.com/id/How-to-make-a-BAT-signal/