I only used a Pi (1B) (20$) 4GB SD Card (5$?) case (6$) and hdmi cable (0.5$)
My TV has HDMI CEC built in which means my tv remote works with the OSMC / Kodi / etc install.
This gets me to a total of 31.5$ for my full HD supporting mediacenter :)
(the case is even optional since it sits on the back of my TV, out of sight)