From now until 4 Jan 2018, you can purchase 150000 AAdvantage miles, and receive a bonus of 120000 miles, at an overall cost of 1.77 cents per mile.
The minimum number of miles that you can purchase is 10000 miles. Also, do take note that the bonus miles offered are tiered, meaning that you will get better value the more miles you purchase.
Here is a list of destinations and corresponding miles required when travelling out of Singapore, should you wish to redeem your AAdvantage miles for award travel.
Personally, I am more inclined to travel on Singapore Airlines and Star Alliance partners, so Lifemiles sales tend to be more appealing to me. But that being said, if you are a frequent traveller on the One World alliance, then this sale may be of use to you.