I have a Deere SST16 that I bought in 2000. I'll be moving in the fall and won't need it at the new place. It runs fine, but looks somewhat rough. It also could use a new mower deck, although the old one still works. Anyone have an idea what a fair asking price would be?

Googled https://www.unitedagandturf.com/used-equipment/
2001 = $2150 373 hours

Many places to list it, adding Or Best Offer
then let us know the final selling price?

Ya good luck with that. And this from the people that offered my friend $200 trade in for his in nice condition to buy a current fancier one. Lots of parts machines sold in $300 price range this past year, one with nice but needs work on deck label for $390.
Here is that one and another listed today
https://www.machinerypete.com/other/lawn-and-garden/john-deere/sst16
I suspect $500 one will sell long before $2150.
I spent probably $750 on tires, belts, blades, hubs, hoses, filters, fuel pump deck wheels and misc stuff to put a similar age high end cub cadet back in acceptable operating condition with me doing welding and labor. And there is no way I could sell it for what the (Chinese) parts cost.
It's worth something, and unless if beyond pristine condition its not $2150.

Thanks for the responses. I expect I would have to be delusional to ask anything approaching $2150, but the $300-$500 range might be doable.