Are frequent flyer credit cards worth the plastic they're printed on?

We've been wondering. Does it make sense to spend $25,000 on a frequent flyer credit card in order to earn 25,000 miles, which is typically what you need for a free domestic roundtrip ticket. If, that is, there are seats available to frequent flyers, which there often are not.

All too often, you have to spend 45,000 or 50,000 miles for a domestic ticket, right?

And what if that ticket would only cost you $179, or $225, the typical price that we often list for cross country fares when there's a sale?

Maybe you'd be better off with a cash back credit card instead. For example, after you've spent $6500 using your card, the American Express Blue Cash card pays 1.5% on all purchases, and 5% back on supermarket, gas station, and drugstore purchases. So let's say you take that same $25,000, and let's say $15,000 of that is "other" purchases, and $10,000 is gas, food, and drugstore.

The calculator please! You'd earn $225 plus $500 for a total of $725 in cash back. And then you take that cash and buy yourself a nice airline ticket without being told, sorry, there are no seats.

Honestly, seems like a no brainer to us.