Should I buy this DTW-BOM itinerary using miles or cash?
 

So I’m looking at a DTW-BOM flight on Nov 30 that’s 49,500 UA miles on United. I currently have only 42k miles in my UA account.

I can purchase the additional 7k miles for $280 but considering the cash price of the ticket is just $1k, it seems crazily disproportionate to spend $280 to cover 1/7th of the ticket’s cost in miles.

Am I better off preserving these 42k miles for a future flight and spending $1k to buy this ticket in cash?

Cash versus miles is entirely personal. We don't have access to your financial records, so it's impossible to make an eveluation in your personal situation.

The $1k ticket vs. 49.5k RDM is 2 cpm redemption value, which is decent.

The $280 7k RDM purchase essentially means you are trading $720 additional outlay vs. 42k RDM. That changes the redemption value to 1.7 cpm. It is clearly less good but still acceptable.

Will you be able to get more than $720 worth of value by redeeming your 42k RDM on another trip? If so, then do that. But best advice is don't save the miles for some unknown hypothetical trip that may never happen.

You have to book the flight to see it. It will appear on your itinerary screen after the flight is booked. Something like “need extra miles for your next trip?”

Don’t forget to cancel the flight once you’ve made a decision on buying the miles. :)

A 1.7 cpm redemption in economy is good for United miles, especially for a less frequent traveler. I'd say go for the miles option.