Just look for sales on frequent flyer miles and buy enough to get a one-way award. For example, American often has sales where the end cost of a AAdvantage mile is around US$.02 or a bit less.

Even if your travel dates aren't flexible enough to gamble on a business class "saver" seat coming open (57,500 miles one way) and you have to buy an "anytime" award (generally always available/every flight,) that's 110,000 miles, so at 2c per mile that works out to $2200 or so for a one-way seat, anywhere in N. America to anywhere in Europe (must use AA metal over the water.)