from a cents per mile CPM view: miles are traditionally considered to be worth 1 to 2 cents each.

Prices just before recent tax, fee, fuel surcharge and award mile increases (DL going from 50K to 60K TATL), forgetting minimal taxes:

25K miles for a domestic you could buy for $250 = 1 CPM
50K miles for a TATL you could buy for $1000 = 2 CPM
100K miles for a TATL WBC you could buy for $5000 to $10,000 = 5 to 10 CPM return for spending your miles.