In June, I opened my US Airways Master Card, which gave me 30,000 miles after my first purchase. In August, US Airways had a sale of frequent flier miles: buy up to 50,000 miles and get the same amount for free. As it costs 90,000 miles to travel between North America and North Asia in business class, I purchased 30,000 US Airways miles for $1,200 and got the final 30,000 miles for "free."