American billionaire John Malone, chairman of the cable and telecom giant Liberty Global, snapped up 427-acre Humewood Castle in Kiltegan, Co. Wicklow, for just $11 million (€8 m) last year - about a third of what it sold for in 2006.
But he told the New York Times :"I didn't buy Humewood as a financial investment. It's an act of love rather than financial acumen."
James E. Thompson, an Irish American based in Hong Kong who runs the Crown Worldwide Group fell in love with Woodhouse, a country home on 400 acres in Waterford, and bought it reportedly for one third the former price .
Cash-rich investors from the U.S. now make up the bulk of buyers of the country's "bargain-priced" stately mansions.
According to property watchdogs, high-end properties on vast estates are now changing hands for about a third of 2007 levels.
Charles Noell, also of Irish ancestry from Baltimore and head of the firm JMI Equity, snapped up Ardbraccan, an 18th-century mansion in Meath.
Noell paid $6.3 million, one third of the asking price seven years ago.
Since the crash, overseas buyers have stepped in to fill the void left by bankrupt Irish developers and speculators.
Harriet Grant, head of country house and estate sales at upmarket broker Savills Ireland, told The New York Times: "It's been really interesting, because we didn't really have American buyers in our market for many years.
"You might in one year have 10 [high-end estates] available. But after four or five years of absolute stagnancy in the market, prices have come down to a level deemed to be good value. The economy is steadying and suddenly you have international buyers taking note of Ireland."
David Ashmore, director of Sherry Fitzgerald, said overseas buyers accounted for nine of the top 10 sales of Irish country mansions last year.
He said the trend has continued throughout this year, "with Americans leading the way, although there is emerging interest from Asia and in particular China and Japan".
And because many of the high-end properties have gone into receivership since the crash or have been put on the market by owners who are desperate to repay their bank loans, the asking prices have been slashed.
Jim Clery, a partner with KPMG Ireland, said country houses that would have sold for 3 or 4 million at the market peak are available at a million or less now and selling.
However, buyers have been warned to factor in the running costs of their newly-acquired mansions.
Roseanne De Vere Hunt, head of residential and country properties at Ganly Waters, said: "The Irish Americans who come to view castles for purchase have a lovely two or three days looking in the country and travelling in Ireland, but then the situation hits them.
"These historic properties require a lot of renovation work and constant maintenance."