Through October 31, 2012, American is offering tiered bonuses on the purchase of AAdvantage miles, as follows:
As you can see above, the bonuses vary based on the number of miles purchased, with a maximum of 10,000 bonus AAdvantage miles when you purchase 36,000-40,000 AAdvantage miles.
Crunching the numbers, through this promotion you can purchase a maximum of 50,000 AAdvantage miles (40,000 base miles plus 10,000 bonus miles) at a cost of $1,212.50, for a total of ~2.4 cents per point.
That’s definitely not a rate at which I’d outright purchase miles unless I was topping off an account for an award ticket. But if you were going to buy miles anyway or had a specific redemption in mind, this is definitely better than the standard offer. If you’re just looking to “invest” in some miles, US Airways’ current “share miles” promotion is much more compelling.