It's a bit old news, but the recent sale of Fund.com for incredible $9,999,950 USD is the highest confirmed all cash sale of a domain name until now..
The details of the sales was officially released just a few days ago, but the domain was purchased in January 15. this year, and the purchase agreement had been signed already in October 2007.
From their press release:
Under an Asset Purchase Agreement dated October 1, 2007 and filed in a Form 8-K report with the S.E.C. on Jan. 15, 2008, Eastern Services Holdings, Inc. purchased the domain name Fund.com along with associated intellectual property (details of intellectual property not divulged in filing) from FST Limited for a total cost of $9,999,950.
With the new acquisition Eastern Services Holdings, Inc. has officially changed its name to Fund.com, Inc. (OTCBB: FNDM.) http://www.free-press-release.com/ne...204236379.html
More about this sale on DNJournal:
http://www.dnjournal.com/archive/dom...es03-18-08.htm
The last "King of domains" was Porn.com that was sold for $9.5 million in May last year.
The sale of Sex.com may be higher, the final sales price has never been officially released but it's believed to be around $12-$14 million (some in stocks).
Other verified large domain sales that can be worth to mention are:
Diamond.com, for $7.5mill in 2007 ($6 mill in 2000)
Beer.com, for $7mill in 2004
AsSeenonTv.com, nfor $5.1mill in 2000
Shop.com, nfor $3.5mill in 2003
Vodka.com, for $3mill in 2006
CreditCards.com, nfor 2.75mill in 2004
And no, I refuse to add Business.com to that list, even if Guinness Book of Records have listed it as the most expensive domain name of all times for several years now.

The sales price is listed as $7.5 million USD (in 1999), but "only" around $500,000 of that was in cash, the rest was in stocks and we all know how very stable (or not) the "internet stocks" were back around Y2K so it's quite hard to calculate the exact sales price of Business.com...