For a staple, it certainly is expensive (that is, unless you make your own at home). For the millions who want to grab a cup on the go, the price for a single cup 'o joe can reach $5 or more. If gas cost as much, it would be $32 per gallon. Still, it's one of those luxuries some spend hundreds of dollars on unknowingly.
Here's the thing: how many of you actually know what you're ordering? Macchiato, americano, breve, cappuccino, mocha… there are so many. Or do you just give up an order a vanilla latte (the most boring drink ever conceived).
Want to find out? Check out this image; it breaks down the most common coffee constructions. I knew what some of them were, but I now understand why I don't prefer americanos, and why mochas are so sinfully delicious.
The point is, know what you're buying! Do you feel like a dork for dropping $4.25 on a marshmallow-flavored latte when you can get the same basic effect with a shot of espresso (or house brew, which is usually even cheaper), half-and-half, and a couple of dissolved marshmallows? I certainly do.
Whatever you decide on--and there are a lot of coffee brewing options--do it on purpose, instead of naively buying the equivalent of a gilded pencil.