Last week DNJournal reported that free.games sold for $335,000.
I believe this is the highest new top level domain sale between a domain investor and a buyer. There have been larger public sales but they were directly between the registry and buyer.
CentralNic Group Plc (LON:CNIC) provides registry services, distribution, and strategic consultancy for new TLDs, ccTLDs and SLDs. They uses their in-house developed IT platforms to distribute its portfolio of popular domains to a global network of over 1,500 registrars (retailers such as GoDaddy LLC), which sell these to end users.