United just sent out a targeted offer, likely for those that purchased miles last year, to purchase up to 100K miles at 40% off of the usual price.
This offer is valid only using the from the email that United sent and the Mileage Plus number is embedded. I cannot provide a link for this purchase. For those that received this offer, must make the decision to purchase or not the miles by midnight CST on February 18, 2013.
You can get the maximum 40% discount IF you buy more than 40K miles.
The price of the United mile, when purchased in greater than 40K miles lot, is 2.26 cents each. United has been selling unlimited award miles for 2.1 cents by taking advantage of the Award/Premier Accelerator that I have written about.
I value United miles higher than US Airways or American Airlines ones. This is mainly due to flexibility with transits & routing rules, number of Star Alliance carriers and stopovers.
You can have a double open jaw + stopover in return itineraries. I am also a huge fan of being able to book most of the award itineraries online at United.com without having to call reservations.