Delta is offering a 50% bonus on transfers of mileage from one account to another by January 31.
The most miles you can transfer at a time is 30,000 and the cost is 1 penny per mile plus $30. You can thus ‘buy’ 15,000 bonus miles for $330.
Not worth it to me, I won’t ever do this for a bonus of less than 100% (which they’ve offered in the past) just for the sake of accumulating miles.
On the other hand, if you’re short miles for an award and you have a friend or spouse with some orphan miles this is one way to top off towards a specific redemption.
It’s useful if you have family or friends who don’t really collect miles. Maybe they have 5k or something which you know will expire. You’re basically “buying” their stray miles, so the total transaction comes out to under 1.5c per mile.