I have one of these boxes but think I paid possibly a good deal less.
These units are incredibly useful at whatever price.
Their stop library and configurability is supreme so if you want a particular stop on pedals, or great, or Positif, it's there. The Baroque reeds are really super.
They also provide a wonderful opening to experimenting with temperaments and their tuning adjustment makes synchronisation with temperature dependant pipe pitch easy if one wants to add to the versatility of a pipe organ
Good luck with your sale!