You can buy or gift the maximum number of 50K miles per account that is then doubled to 100K miles. If you buy the maximum number of miles allowed through this program, the price of a mile is 1.88 cents.
Please note that the promotional code for this short December offer that was extended from November is different. So, if you participated last month, you may take advantage of this December offer as well.
This is one of the never ending promotions for buying US Airways Dividend Miles that you can turn to premium international wards on Star Alliance carriers.