Well I couldn’t really believe it when I found it, but an original Sinclair ZX Spectrum, hidden in an attic. Even with plastic coating left on. This particular model was advertised as amazing with just 48k of RAM!A quick bit of research from wikipedia gave me a bit of information on what it cost and how revolutionary it really was:
The original ZX Spectrum is remembered for its rubber keyboard, diminutive size and distinctive rainbow motif. It was originally released on 23 April, 1982 with 16 kB of RAM for £125 or with 48 kB for £175; these prices were later reduced to £99 and £129 respectively. Owners of the 16 kB model could purchase an internal 32 kB RAM upgrade, which for early “Issue 1” machines consisted of a daughterboard. Later issue machines required the fitting of 8 dynamic RAM chips and a few TTL chips. Users could mail their 16K Spectrums to Sinclair to be upgraded to 48 kB versions. To reduce the price, the kB extension used eight faulty 64 kilobit chips with only one half of their capacity working and/or available. Links on the PCB were configured accordingly so as to place these faulty memory locations in the other (unused) half of each IC. External 32 kB RAM packs that mounted in the rear expansion slot were also available from third parties. Both machines had 16 kB of onboard ROM.
About 60,000 “Issue 1” ZX Spectrums were manufactured; they can be distinguished from later models by the colour of the keys (light grey for Issue 1, blue-grey for later models).
The Sinclair models all had audio line in and out, in the form of an “ear” and “mic” socket. An external tape recorder was needed to load the majority of software released. Either socket could also be connected to headphones or an amplifier as an audio output, though this would not disable the internal speaker.
And the best part it still works 30 years on, if you can find a screen with analogue video and audio ports that is.