I have flight booked for 75,000 miles. I have a few minutes to decide it it's worth paying money to transfer to a 60,000 mile flight. Does anyone able to tell me the worth of those 15,000 united airline miles_ is it worth the money to transfer? It costs $100. I guess to sum up my question- which has more value: $100 or 15,000 miles. What's the dollar value of a single mile?