Through December 31, American is offering a 2,000 mile bonus for every 6,000 miles purchased, with a cap of 20,000 bonus miles (for a total of 60,000 purchased miles, plus the 20,000 bonus miles). Through this promotion you’re paying just a bit over two cents per mile. While I don’t think it’s worth taking advantage of the promotion just to buy miles, this is a pretty goal deal for topping off an account so you have enough miles for a specific award. Or in many cases if you have a specific award in mind, this might make sense too. For example, a one-way business class ticket to Asia costs 55,000 miles, so through this promotion you would be paying about $1,200 for that ticket. Not bad!
The bonus miles post 6-8 weeks after the promotion finishes.