American is offering 2000 bonus miles per 6000 miles you purchase, up to 12,000 bonus miles total, through November 15th.

That works out to be a one-third bonus (as long as you buy the right number of miles).

That’s still too expensive, in my view, unless you specifically need to top off towards a particular award.

Here’s how the cost breaks down:

• 36,000 miles purchased earns 12,000 bonus miles, for a total of 48,000 miles.
  
• That purchase costs $990 + 7.5% tax + $35 transaction fee, for a total of $1099.25.
  
• That comes to 2.3 cents per mile.

Now, I value American miles highly. I love them for international first class awards on Cathay Pacific, Etihad, and British Airways (this last with fuel surcharges). And their distance-based awards can offer tremendous advantages.

But buying an award at that price is just costly — you can’t buy 100,000 miles this way, but if you could it would be $2300 for a transatlantic business class ticket (plus taxes on the award) and that’s subject to capacity controls more restrictive than an advance purchase off-season business fare. Just doesn’t compare favorably.

I think that miles need to be under 2 cents before I’ll consider a straight-up purchase. Even the 100% bonus on US Airways miles is a little pricey for me at almost 1.9 cents a mile.

Still, some will value this — for instance if you’re just short of having enough miles for a premium cabin international award, the extra cost for a few miles can make sense.