United is offering a targeted bonus on purchasing miles through March 23, 2015 that varies from 20 to 50%. Check your email for the subject line: “Reveal your bonus: Receive up to a 50% bonus when you buy or give miles”

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When I clicked “Reveal my bonus >” in my email, I learned that my bonus is 25%.Screen Shot 2015-03-11 at 9.03.34 PM

United miles cost 3.76 cents each. With my 25% bonus, they cost 3.01 cents each. If you get a 50% bonus, your miles will cost about 2.5 cents each.

Screen Shot 2015-03-11 at 9.04.22 PMIs even 2.5 cents per United mile a good deal?

No. I value United miles closer to 1.7 cents each, so I certainly wouldn’t load up on them at 2.5+ cents per mile.

The answer is almost always the same on buy-miles promotions:

It is a bad deal to speculatively buy the miles without an immediate use. Not only are United miles not worth 2.5 cents in the abstract, but miles can always be devalued before you use them. However, if you have an immediate use of United miles where you get more than 2.5 cents of value–achievable–this is a good deal.

Better Deal: United Miles for 1.9 Cents Each

Mommy Points explains how to add Premier Accelerator to a cash ticket purchase on united.com to buy miles for as little as 1.9 cents each. Then you can cancel the cash ticket within 24 hours for a full refund if you’d like. The miles purchase is non-refundable.