Delta's nominal price is 2 cents/mile, but they have frequent promotions where if you buy enough miles they throw in some more "free." Typical numbers are pay for 150,000, get 175,000, which cuts the cost to just over 1.7 cents/mile. Other than the US$3,000 cost to qualify for the bonus, the biggest problem is that you can't give more than (I think it's) 25,000 to any one person in the same calendar year.