I don't have a tremendously refined sense of taste when it comes to coffee, but I honestly can't tell the difference between pre-ground Folgers and freshly-ground Starbucks or between percolated and drip.
I can. The Folgers will taste better. Starbucks, and most "gourmet" coffee houses for that matter, overroasts their coffee. A good medium to medium dark roast, enough coffee for the amount of water being used and you'll get a good cup. You can get good (or at least drinkable) results with cheap coffee, but you can easily ruin good coffee with bad form.
I was basing my estimate on the assumption that most people don't go to Star Schmucks for a plain coffee.
The only time I buy anything other than plain coffee at Starbucks is when they're offering their holiday themed Gingerbread Latte. I hesitate to call it coffee given the amount of sugar, milk, and flavoring, but it's pretty dang tasty to me. My wife, not a coffee drinker at all, like's it too. During the Christmas Holiday, we'll spend about $10-$15 between the two of us on these concoctions. I don't spend that much the entire rest of the year at the place.
Chris