At the end of my world tour, I will likely reserve a one-way flight from East Asia to the United States. For example, let us presume that I want to fly from Narita International Airport (which serves the Tokyo area) to San Francisco International Airport in May 2015. The least expensive round-trip flight may cost a reasonable $1200, but a one-way fare may price at $750. Half of a round-trip fare would be $600 so I feel rightly that I am paying a tax of $150 for booking only a one-way fare, due to complex airline reservation rules.
The two most useful frequent-flyer programs for transpacific travel are United Airlines’ MileagePlus and American Airlines’ AAdvantage. MileagePlus charges 35,000 miles to book this one-way fare. AAdvantage charges only 25,000 miles. By using mileage redemption for a one-way fare such as NRT-SFO, I can avoid the cash tax incurred from not booking a round-trip flight.
It is important to be aware of all the options in booking any route: mileage redemption; large carriers; and low-cost carriers.
Low-cost carriers do not serve transpacific routes. The cash fares are such so that one-way flights usually price at more than 50% of round trips, whereas mileage redemptions have fixed values.
A route like Bangkok-Singapore has many low-cost carriers serving it, so this route would be a poor use of mileage redemption since the out-of-pocket cost could be less than $100.
Almost all domestic United States flights price one-way fares at 50% the cost of round-trip bookings. Due to this flexibility, I usually refrain from domestic mileage redemptions because I want to save the miles for one-waying around the world.