The Arduino platform is (for better or worse) a widespread, well-known, and overused way for beginners to get into microcontrollers and smart electronics. For this reason and others, I chose it as the core of the original gCn Bridge design. For about $30, you get a reusable microcontroller board, USB-serial interface, and more. However, I've heard plenty of noise from the community that $30 is a bit steep for some of your budgets, and I personally have thought that I don't want my Arduino board to be forever stuck being a gCn bridge, since it's meant to be a bit more reusable. Therefore, I've been designing a so-called "$10 bridge" centered around a raw AVR bitbanging USB HID thanks to the V-USB drivers (or more specifically, V-USB for Arduino). Sadly, I have not yet succeeded getting the USB bitbanging up and running, although I have been able to successfully run the gCn Bridge calculator-AVR code and seen its successful results via debugging LEDs. I have been posting some updates on a Facebook status of mine and getting feedback from the inimitable Ben Ryves; I'll be switching to this topic now. A preliminary parts list:
(1) Atmega328p with Arduino bootloader (needs to be programmed, though, so you at least need access to someone else's Arduino just to program it) [$5.50]
(1) 16MHz crystal oscillator [$1.25]
(2) 22pF crystal loading capacitors [$0.25 each = $0.50]
(4) 330 ohm resistors [$0.10 each = $0.40]
(1) standard LED [$0.20]
(1) RGB LED [$1]
(1) 2.2K ohm resistor [$0.10 each = $0.10]
(1) 4.7K ohm resistor [$0.10 each = $0.10]
(2) 68 ohm resistors [$0.10 each = $0.20]
(1) pushbutton [$0.45]
(2) 3.6V Zener diodes [$0.10 each = $0.20]
Total cost: $9.90
This doesn't include breadboard, USB socket (or cord cut apart), PCB, solder, or IC socket for the Atmega.
And to finish off, a picture of my currently very messy breadboard as I've been trying a few ugly hacks for your curiosity and mockery:
(1) Atmega328p with Arduino bootloader (needs to be programmed, though, so you at least need access to someone else's Arduino just to program it) [$5.50]
(1) 16MHz crystal oscillator [$1.25]
(2) 22pF crystal loading capacitors [$0.25 each = $0.50]
(4) 330 ohm resistors [$0.10 each = $0.40]
(1) standard LED [$0.20]
(1) RGB LED [$1]
(1) 2.2K ohm resistor [$0.10 each = $0.10]
(1) 4.7K ohm resistor [$0.10 each = $0.10]
(2) 68 ohm resistors [$0.10 each = $0.20]
(1) pushbutton [$0.45]
(2) 3.6V Zener diodes [$0.10 each = $0.20]
Total cost: $9.90
This doesn't include breadboard, USB socket (or cord cut apart), PCB, solder, or IC socket for the Atmega.
And to finish off, a picture of my currently very messy breadboard as I've been trying a few ugly hacks for your curiosity and mockery: