The Raspberry Pi Foundation has released their newest, smallest and cheapest device yet: The Raspberry Pi Zero. And all it cost is a measely $5. Here's the specs on this tiny little fella:
A Broadcom BCM2835 application processor
1GHz ARM11 core (40% faster than Raspberry Pi 1)
512MB of LPDDR2 SDRAM
A micro-SD card slot
A mini-HDMI socket for 1080p60 video output
Micro-USB sockets for data and power
An unpopulated 40-pin GPIO header
Identical pinout to Model A+/B+/2B
An unpopulated composite video header
And ab absurdly small form factor of 65mm x 30mm x 5mm
It's not a fast setup by any means, but it does have enough juice to run a lightweight kodi setup. It's not quite $5 as you likely also need a mini usb and mini HDMI adapters, which you can score as a bundle in the raspberry Pi store for another $5.
A major issue is the lack of wifi or Ethernet on the board, making it used more for local media playback unless you jury rig your own connectivity solution. Realistically if you're looking to run kodi on the Pi platform you're better off using the Pi2.