Avianca LifeMiles is offering a 125% bonus on purchased miles, today only. This brings the price per mile to 1.47 cents per mile. That’s a good rate, but probably not worth buying unless you have a specific use in mind. Anyway, if you’re interested here’s the link.
Purchase 10,000 miles, get 12,500 free. Total cost: $330. Cost per mile: $330 / 22,500 = 1.47 cents per mile.