I believe a majority sales on dnjournal are not reported (and to be fair they do do state that) i have never had any of decent sales posted on there which are for $10K,$12.5K,$15K all private and i am only small time so there must millions of dollar worth of domains unreported ?
Of course.. its tip of the tip of the iceberg sort of stuff.
Only a few pecent of sales will be known, mostly because they were sold through a domain selling medium and the sote owner wants some good exposure.... nothing more that that really.
People who sell domains privately and then report the sale are surely just trying to massage their ego and show how clever they are.
On the flipside, the only reason a company would be willing to tell the world they paid a fortune over the odds for a domain name is for exposure themselves. Thus, we see very little of the true sales picture.
Country code sales in particular are scarcely reported though there are undoubtedly many.