Originally Posted by
GetawaysRus
... The cost of the ticket divided by the number of miles needed to obtain that ticket gives you the cost per mile. ...
... As an example, early this year we traveled to South America. A round trip J class ticket to my destination in S. America on AA "costs" 100,000 miles. It was priced at $5500 on aa.com at the time I made my reservation. That's 5.5 cents per mile. (Just remember that I might have been able to buy that ticket for less through other sources, or it might have gotten less expensive as my travel date got closer, so 5.5 cents per mile may be an overvaluation.)
You really have to take into consideration that you would have earned miles if you had bought that ticket at the price you find on AA.com. A trip from the US to South American might have given you around 10,000 miles in your AAdvantage account, so you might be really giving up 110,000 miles, not just 100,000 miles for your ticket. Of course, the number of miles earned depends on elite status, promotions, etc. Nonetheless, dividing $5,500 by 110,000 miles works to to 5.0 cents per mile instead of 5.5 centers per mile. Although it gets difficult to quantify, you are also giving up elite qualifying miles that could qualify you for elite status for next year, life-time miles that could qualify you for retirement years, miles that might give you a year end bonus, etc. The complete calculation depends heavily on individual circumstances.