When to use miles vs. purchasing a ticket
 

Flying from MSP - LGA. Miles would be 25K + $5RT. Whereas, the flight would total $280RT. At what cpm is it best to buy the ticket instead of using miles or vice versa?

I prefer saving up mile for transcon flights and $280 for that leg is pretty reasonable. Think about it this way...if you did this trip 4 times it would cost you either $1,120 or 100K miles and $20. 100K miles (plus taxes and fees) gives you a business class award ticket from North America to Europe on certain airlines (US for certain) which you definitely can't get for $1,120.

only you can decide.....divide ticket price less cost of fees by mi's to get the mi value....

in your example, you could go 1st for 25k more mi which would a better value per mile....

if you are out of work, keeping the $280 might make sense....

good luck...

There's no right or wrong answer.

I look at which I have more of at the time, miles or money. If I have way more miles then I do money, I may use miles for it, even if it's a short trip.

To me the cost per mile just doesn't matter. I can only use the miles (pretty much at least) on tickets and upgrades. The money I can do lots with.

It all depends on what you want. I have written a few blog posts on this very topic. Check 'em out:
- The Value of Airline Miles
- Never fly for free

With the imposition of copays for international upgrades on American, I've generally found that it's a better value to cash in miles for premium class directly than to get a coach seat and upgrade.

Similarly, coach is sometimes a very good deal; 40k miles + < $100 in taxes is a very bad deal when off-season London tickets are around $500 - it's starting to look like a good deal when Buenos Aires tickets run around $1000, even if you account for the lost miles, and while it's unusual to find a low-miles ticket when the fares are above par, it's not entirely unknown.

It also depends on how you balance EQM vs. RDM - in general, I earn RDM faster than I use them, and save them for "big bang" trips with my wife. OTOH, the value of keeping PLT is personally very high and having a year I can make EXP looks unlikely - so on years when I expect to make PLT easily, my goal is generall to minimize my cost of EQM up to that limit, and replacing a pricier flight or two with award tickets (as I did for one in 2009) makes a lot of sense.

Similarly, "fly this route twice, get the third free" (with PLT bonus RDM) makes a lot of sense for some folks I know.

OTOH, neither one is necessarily the best way to maximize the cash-out value of your RDM.

I value miles at around 1.5 -2.1 cents per mile (I redeem solely for coach award tix since I am not a big earner like many people on FT). This valuation is just based upon my own personal experience booking award tickets and looking at what it would have cost me to fly the same flight using cash.

I tend to fly on paid tickets until I've requalified for whatever status level(s) I can reasonably reach that year, then on awards. Those are flexible guidelines: if I can get an award seat that would otherwise be expensive, and I expect enough lower-cost travel later in the qualification year to get the job done, I'll go for the award. However, requalification trumps almost anything else.

Having just returned from a round trip from the northeast U.S. to India over the Pacific, I would not have wanted to be without faster check-in, lounge access, priority boarding to get overhead space, and all the other stuff (which in this case included an MAA-SIN operational upgrade followed by a personal escort through Changi to make an otherwise impossible connection after a departure delay). I don't mind flying in back, though obviously F/J is better, but I would NOT want to be without status! After 20+ years, I'm spoiled that way.