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CHIP - 9$ single-board computer
It's not funny. Really, single-bord computer costs $9.
The website shares project of single-board computer - CHIP (as Raspberry Pi) which costs $9. Doesn't have poor performance.
1GHz A13 ALLWINNER, 512MB RAM and 4GB NAND flash. And more one USB, WiFi 802.11b/g/n and Bluetooth 4.0.

Do you want HDMI? Add HDMI board on CHIP board. OS is debian and the project is open-source.