This domain is owned and maintained by Mark Minasi. It was once my main domain when my firm was "Mark Minasi and Company," but now I keep it because I've had some "@mmco.com" email addresses for, well, a really long time and it'd be a pain to move them, and besides, Mark Minasi & Company still has its hands in a few pies.
That said, the fact that this domain is (1) four letters and (2) ends with "co" makes it a mite rare, where here "rare" means "there are only 675 others." So because I get the question "will you sell this" pretty regularly, the answer is $15,000
(Oh, and by the way, if there's a spammer out there that claims that it's now okay to email me with unsolicited commercial email -- spam -- because this is on a web page then sorry, it's not, and I specifically forbid it in any case. That said, if a spammer were to send me some junk email, then, well, let's say that I have a close relationship with all of the spam blocker lists.