The Raspberry Pi is a credit card sized computer that plugs into your TV and a keybord. It is capable little PC which can be used for many things that your desktop PC does. It can do spreadsheets, word-processing and games. It can also play high-definition video.
Minecraft is only released on Xbox360, PC, MAC, iTunes, Android, and RaspberryPi.
Computer chips have been falling in cost by Moore's Law since 1960. By 2020 they will cost 1p each. You can buy a basic board with chips on RaspberryPi for £16 ($25), you can buy them for 32p (47c) You can factor back from 2020 1p chip to now by doubling that every 18 moths...ie 1018 6 months 2p 2017 4p 2015 6months 8p 2014 16p 2012 6months 32p