I would not recommend buying miles at 3 cents, and at 2.5 cents you should have a compelling reason, like topping up your account for an award. (travelcodex.com)
After you've created an account, you can top up your account with digital currencies right away. (wirexapp.com)
If you need more miles more quickly than you can earn them via credit card signup bonuses, you may want to top up your account by buying AAdvantage miles. (travelsort.com)