Many airlines are having sales today. Here's a roundup:
American Airlines: 1.77 Cent Miles
American Airlines is offering up to 120,000 bonus miles for miles purchases made by Monday November 27, 2017. If you buy the largest amount possible, you can get the miles for as little as 1.77 cents each. We saw them on sale for 1.72 cents in July, so this isn't even the best deal of the year.

Bonus miles are tiered based on how many miles you purchase.