Those were not IDN, but mostly english.cn. Not sure if you remember but you could register them at one point for under $1 and some took the bait, but did not go for the "rack rate renewal when that came around.
I would expect idn.cn to drop as well based on the erratic behavior of the Chinese government "taking" domains that they don't like, or restricting use etc. Also the $35 a year registration fees are high considering the ris, even if you get the different variants of simplified and traditonal characters.
There is more activity than you might imagine but most IDN sales happening mostly under the radar....I sense that most are low to mid xxx sales range but nonetheless this is stuff people handregged in the last 3-4 years so a nice ROI.
DNJournal reports of a $10,000 sale of a Hindi idn: à¤à¥à¤¸à¥à¤¨à¥.com ....said to be the first 5 figure sale of a Hindi IDN.
http://www.dnjournal.com/archive/lowdown/2011/dailyposts/20110408.htm
QUOTE: This week I learned that the first known five-figure sale of a Hindi IDN domain name was made late last year, however seller Steve Clarke just now got clearance to release the details. He got $10,000 for à¤à¥à¤¸à¥à¤¨à¥.com (puny code: xn--11b2b6b6a0bv.com) - which means "casino" in Hindi script. END QUOTE