I think this kind of sales were more frequent some years ago, when the domain industry were younger and not so crowded.
Now i see "too many" domainers (especially beginners) and also considering the web evolution (i think we're going to talk about web 3.0 soon), the value and, most important, the appeal of the "generic" domains dropped drastically.
Those of you who remember years like 2007 - 2008 (when i started), it was way easier to manage a profitable domain sale.
My domain was a .in one, with the word "india" in it.
Registered at the end of November 2007 (sorry, checked better now) It was enough to post on some forums (most of them are dead now, i think i didn't post it on here for example, if i remember well, the "push-to-auction" thread weren't allowed years ago) i had this domain for sale on Sedo, and few days later (around Christmas) i received the first offer.
The auction reached low $x,xxx and ended just in time to wish a good domaining year to me (and it was!).
I remember i did it again the same, and received a offer on Sedo within 1 day (another .in with "india" inside), auction ended high $xxx. Also i remember i was able to catch dropped domains for reg-fee and flip them for high $xx - low $xxx within days or sometimes hours. I remember i won a Snapnames auction for a LLL.info for $120, and received an offer like 5 hours later for $300. This wasn't so rare as it is now.
Then the 2008-2009 crisis. During last years a lot of people have been attracted by all those $xx,xxx sales and joined this industry, and i'm not sure this is healthy right now.
Indeed i'm quite sure, guys, all these $x,xxx reg-fee sales we're talking here aren't so much recent.