I did, too, for years. I used a single-cup cone and filter with freshly ground beans. There's really not much difference, and the Keurig approach is a whole lot cleaner.
COST: About the same per cup. Unless you buy from the local market for $1.00 a cup, you ought to be able to get the K-cups for about 35 cents or so apiece. Compare this to buying a pound of coffee at fair trade prices (about $13.00 per pound where I am) and for a single cup a day you go through about that much. You're going to pay some serious money for a good grinder (not those horrid centrifugal force pieces of crap that break every year) the same as you'll pay for a Keurig machine. So on a cost per cup basis if you're a single-cup-person, it's about the same cost to run either way.
QUALITY: If you're getting "watery goop" (as one said here) change your brand. K-Cups can brew excellent quality coffee--or not--your choice. Shop around and go for "bold" brands and you ought to do fine.
CLEANLINESS: Keurig hands-down. No muss, no fuss. No time needed. Spill a cone full of hot coffee and you've got yourself a disaster. Been there; done that more than once. Unless you have hard water, Keurig runs clean.
I've had my Keurig for two years or so after having done the cone atop the cup trip for several decades. I spend no more on coffee than I used to. For those of you who brew pots and drink lots, a Keurig makes no sense and is way too expensive. But if you are content with a wake-me-up cup most days, a Keurig makes a lot of sense and is cost-equivalent to other ways of brewing.