I went through published sales records of NNNN.net's to get a sense of average sale price for these domains. I gathered data on 49 sales, most of which were from 4.cn this year.
Average sale price was $1,197, and the median was $58.
What accounts for the big disparity?
2012.net sold for $49,999 last year on Afternic, so with a small sample size that had a significant effect.
Excluding that sale, the average was $159. The median, however, shows more of what a random NNNN.net is likely to fetch in a sale, since the average still includes some premium sales (e.g., 1888.net for $1,000 on Sedo this year).
The lowest sales figures seemed to be around $30. 3614.net sold for $22.50, and after that the lowest sales were for $30 (7830.net, 3704.net, and 3766.net).