The Pi 4 itself starts at about $30. A case, power adapter, SD card, etc all add a bit to the cost. Expect to spend about $100
The Raspberry Pi 4 Model B is the newest Raspberry Pi computer made, and the Pi Foundation knows you can always make a good thing better! And what could make the Pi 4 better than the 3? How ...
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I built an entire arcade based on the older Raspberry Pi 2, an old LCD monitor, some car speakers, a cheap chinese audio amp, and some high-quality Hap arcade joystick and button components. The Pi was ~$30 at the time, though I had to buy a WiFi adapter, SD card, and some other bits at the time so again I think I spent about $100 on the Pi + its components.
For the rest of the arcade the joysticks were probably the most expensive component at about $35 a piece. Total was about $500 including the plywood and plexiglass. It'll emulate Nintendo, Sega, Playstation etc but it struggles with anything Nintendo 64, PS3, etc or newer.
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