In the condition you describe it will definitely fetch a premium price, but finding someone who wants it that bad is the trick. $2700 seems a bit of a stretch, 1500 might be more like it. Last I saw, ones that were in like new shape asking price was around 1000 dollars , give or take.
Mine is like new ,I don't have the box, I do have the owners manual I copied off the internet and put in a binder. If someone offered me a grand for it I'd take it instantly.
Here's one like new with manual AND printer that sold for only $730.
http://chesscomputer.org/fidelity-elite-as-model-eas/
I have a vintage 1983 Fidelity Elite A/S Chess Challenger that is in perfect to mint condition. I have the original box, manual, and all paperwork. I am the original owner. I may be interested in selling this item. I know the last one I saw on ebay some time ago sold for $2,700.00.