Here's another way to "calculate" the value of a mile:

While I usually use the miles for premium cabins either to Europe or Kauai for hubby and me, I will be headed to England with a friend in February. She used miles on Delta and I used miles on AA. I'm "sucking it up" and saving miles by using a 40,000 mile coach reward.

Best financial use of miles? Probably not. But the value of these miles lies in helping me "sell" my hubby on why I need to go to England for 2 weeks in February.
"But , honey, I can get an award flight and also use up those 2 certs from Marriott that are going to expire in April since we won't be able to use them together."

Value of these miles - Priceless!!!

BTW - both of us got exactly the flights and dates we wanted on both airlines.