The Sinclair ZX Spectrum was a boom and some start of the microcomputer business. The inventor went bankrupt after investing in producing electrical scooters, but the concept remains sound. In images you see his original invention, a Wireless Bluetooth keyboard, and a 'Rikomagic PC,' that can be used with any TV, plugged in the TV HDMI input socket, with just a keyboard and mouse added.
The keyboard shown, that includes a mouse, has enough inner space for the integration of all basic USB plug computer hardware, and just a Bluetooth or Infrared connection would allow using an existing TV as a computer. Costs probably would be in the keyboard range, as for example, micro SD memory cards, there are on sale up to 64 GB, include a microprocessor that can be accessed through the metal connecting bars/pins of memory card.
The 'quid' of proposal is integrating all hardware, and also the software input and peripheral devices' connections inside the wireless keyboard, cooling may be easy just with the appropriate holes allowing for thermal convection from bottom to top, inside-out of computer-keyboard hull; with the adequate added wireless connections, you may have an instant change of your TV unit into a Home Micro-Computer, powerful enough for many needs, and with very low production and purchase costs. Salut +