Xiaomi spent $577,000 for the mi.com domain name

"Popular Chinese smartphone manufacturer Xiaomi has ambitious plans to expand beyond Asia, and as part of its efforts to do so, it has simplified its website domain to Mi.com.
“The new domain is simpler and more accessible to an international audience,” the company said. It added that the newly launched domain also gives a more succinct meaning to the “Mi” brand, which stands for Mobile Internet.
Li Wanqiang, co-founder and VP of Xiaomi, revealed on Weibo that Xiaomi spent CNY3.6 million ($577,000) to purchase the Web domain."

Source:  The Next Web, 22nd April 2014

Facebook paid $8.5m to buy the url fb.com

"How much money did Facebook fork over when it acquired Fb.com last year? A cool $8.5 million, more than 42 times the amount the company originally paid for Facebook.com.
In November, it was revealed that Facebook was launching a revamped version of Messages. It combined SMS, messaging, chat and e-mail into one interface, although Mark Zuckerberg repeatedly iterated that, “It’s not e-mail.”
One feature of the new Facebook Messages is that it assigns you a personalized Facebook.com e-mail address. If a friend sends a message to your Facebook e-mail, you will receive it in your Facebook Inbox. Unfortunately, Facebook’s employees were using the Facebook.com domain for their e-mails already, so they had to switch to another domain, which is why Facebook needed to buy Fb.com in the first place.
Facebook acquired the domain sometime last year from the American Farm Bureau Federation, which uses fb.org as its primary domain. At its annual meeting in Atlanta, the non-profit revealed that it earned $8.5 million on the sale of fb.com, according to Reuters."

Source:  Mashable, 12th January 2011

The sex.com internet domain has been sold for $13m

"The sex.com internet domain has been sold for $13m (£8.2m)
The domain was put up for auction in July 2010 when its former owner, Escom LLC, went bankrupt.
Clover Holdings, an obscure company registered on the Caribbean island of St Vincent, put in the highest bid for the domain.
The sex.com domain has changed hands several times and at one time was under the control of a conman who stole it from its original owner.
The sale will only be final if it wins approval from the bankruptcy court overseeing Escom LLC's affairs. The court will make that decision on 27 October."
Source:  BBC News, 21st October 2010