I have to say my old 1976 Casi Apollo VP2 S100 bus Computer Photography System is worth the most just because only about 300 were made, only a few still exist. Because it is awesome printing 120 column ascii text photographs and because I have one.
Also the fact that it cost over $25k originally makes it seem collectable to me, Now I just need to get a more usefull printer
(the one for the unit and that works more than 10% of the time)
and the original keypad for it and take it back to the state fairs where it belongs making wanted posters.
Sadly I doubt anyone else would find a 31 year old computer portrait system with 8kb of SRAM exciting.
The one big upgrade on this portrait box was the text overlay ability, that alone was a $1500 option, they used to recommend $0.25 a letter to add text and talked of the amazing ability to make your own custom t-shirts, ooh.
An interesting piece of trivia is the name of the Apollo is from the space mission because several of the individuals that helped nasa make the imaging system on the apollo helped make this computer system.