As I mentioned in my post above, I have a Prodigy in excellent condition too (although not quite ‘mint’ --it has tiny scuffs on the end cheeks!).
I currently have it on ebay with a starting price of £525, which seems to be round about the going rate for good ones. Maybe a little more if I’m lucky.
Two things that also affect the value:
Although you say you’ve ‘fired it up, and everything works’, has it been regularly serviced over the years?
The switches can need cleaning to ensure reliable operation, and the oscillator scaling may need calibrating, for example.
Is it a second edition version, with factory fitted external control jacks? Although you can get the earlier units modified, the factory mods are preferred, and make the unit much easier to interface with modern MIDI kit, like the Kenton PRO.
Both of those points, in addition to the cosmetic condition, can affect the value.
A ‘mint’ Prodigy, second edition, with a full service history, would probably fetch around £500 - £700.
At the other end of the scale, a rough one, with knobs missing, and descriptions like ‘only needs a bit of soldering to get it all working’ can, amazingly, still fetch £300 - £400.
And in reality, some of them will never work properly again!!
In truth, places like Ebay seem to set the value, whether we like it or not, and as with all auctions, it will only be worth what it makes on the day.
The Prodigy is a lovely little synth, but it is 30 year old technology…