The Sub-Zero 532 is a discontinued model, so only previously owned units can be purchased. eBay had two listings as of 2015: one for $300 and the other for $2,500.
Two recently sold used Sub-Zero 532 refrigerators sold for $1,000 and $1,099.
Age and condition are the chief factors that determine the price of the used unit. The capacity of this model is 18.8 cubic feet, and it features a side-by-side configuration.
The Sub-Zero website has an information manual available that is dated September 1996, so any used model 523 is likely at least 16 years old, as of February 2015.