The Raspberry Pi is a low cost, credit-card sized computer that plugs into a computer monitor or TV, and uses a standard keyboard and mouse. It is a capable little device that enables people of all ages to explore computing, and to learn how to program in languages like Scratch and Python.
Five Pis in a DORHEA Raspberry Pi case.
Three Raspberry Pis -"Raspberry Pi 4 Model B 2019 Quad Core 64 Bit WiFi Bluetooth (4GB)" - $~150
One Raspberry Pi cluster case - "DORHEA Raspberry Pi 4 B Case, Raspberry Pi Rack Cluster Case Stacking Case with Cooling Fan and Fan Cover for Raspberry Pi 4,Raspberry Pi 3 Model B B+, Raspberry Pi 2 Model B,Pi B+ (5-Layers)" - $~25
Three quality SD cards - "SanDisk Extreme PRO microSDHC Memory Card Plus SD Adapter up to 100 MB/s, Class 10, U3, V30, A1 - 32GB SDSQXCG-032G)" - $~30
Two Micro HDMI Cables - "CanaKit Raspberry Pi 4 Micro HDMI Cable - 6 Feet (Pack of 2)" - $~10
One 5-port gigabit switch - "NETGEAR 5-Port Gigabit Ethernet Unmanaged Switch (GS305) - Home Network Hub, Office Ethernet Splitter, Plug-and-Play, Fanless Metal Housing, Desktop or Wall Mount" - $20
Three (or more) RJ45 network cables - "Cable Matters 5-Color Combo Snagless Short Cat6 Ethernet Cable (Cat6 Cable, Cat 6 Cable) 1 ft" - $~10
Power supply - "USB Charging Station, 8 Ports Multiple Desktop Chargers with PD USB C Charger Port and LCD Display for Cell Phones, Smart Phones, Tablets, and Other Electronics" - $~30
Three USB C Cables - See below - $~10
Total Investment: ~$280