I paid $425, new from a local dealer for the one I have in '95. Don't know if that helps at all. It's a good machine though. I still have it and use it as a back-up.
I'd say expect to be able to sell it for around $200, or maybe $275-$300 for the SL model. You might get more on FeeBay, but the cost isn't worth it IMO. I wouldn't pay more than a hundred if I were only looking to resell. That would give you a bit of wiggle room.
The fact the say Like New & Listed it as the "Pro"
not "Professional" I'm thinking they may have Copied
off the Side Of course they could have Just Abreviated
to save Space.
But the Old one Spells it out & The SL Abbreviates.