American Airlines has a promotion running until Feb 28, 2013 that offers 50% bonus on purchased miles!
- Buy 5,000-9,000 miles = earn 1,500 bonus miles
- Buy 10,000-14,000 miles = earn 3,000 bonus miles
- Buy 15,000-19,000 miles = earn 4,500 bonus miles
- Buy 20,000-29,000 miles = earn 10,000 bonus miles
- Buy 30,000-39,000 miles = earn 15,000 bonus miles
- Buy 40,000-49,000 miles = earn 20,000 bonus miles
- Buy 50,000-59,000 miles = earn 25,000 bonus miles
- Buy 60,000 miles = earn 30,000 bonus miles
It seems the best miles per dollar will be buying 60,000 miles and getting 90,000 miles for $1650. This is 1.8c/mi. Consider that international business class tickets run $4500+, which you could get starting from 100,000 miles. But at the same time, you won't earn any elite qualifying miles if you buy miles to redeem for a ticket!
I'd consider this is mediocre deal but decent if you need to top off some miles.