United is offering a 72 hour sale on MileagePlus miles, and the bonus you earn depends on the total number of people that take advantage of the offer.
The promotion is valid through 11:59PM CT on Thursday, September 5. The thresholds for earning bonus miles are as follows:
So basically if at least 1,500 people purchase a minimum of 5,000 miles you’ll get a 60% bonus. Miles ordinarily cost ~3.77 cents per mile to purchase including all taxes, so factoring in a 60% bonus we’d be down to ~2.35 cents per mile.
I do suspect they’ll reach the 1,500 person threshold, so if they do, is it worth it to purchase MileagePlus miles at that rate? Well, I wouldn’t do so speculatively, but if you have short term travel plans that can be a pretty good value. For example, United charges 70,000 miles one-way in first class between the US and Asia, and you can even route something like Los Angeles to Frankfurt to Tokyo to Bangkok.
Purchased miles post within 48 hours, and the bonus miles will post within a week of the promotion ending.