If the points used for the reservation were from
DVC members trading to another option (Cruise, other WDW resort, ABD trip, Concierge Collection, etc.) the money received is used to "repay" the cost of the exchange.
If the points were points owned by the developer (DVD), the money received goes to the developer.
If the points used were from "Breakage" inventory (DVC dates unreserved 60 days prior), the money received is returned to the owners at that resort to reduce their maintenance fees. This is found in the annual budget as income under "Breakage Income". There is a limit on how much is returned to owners, but it is a pretty substantial amount each year.