I work with a team, but I'd say for a page start to finish it's about 10-12 hours. The writer and I spend quite a bit of time thumbnailing first (and however long it takes her to write the story), which I think speeds up the process. However, its a couple of hours for sketching pages then inking them, a few hours for my partner to color flats, then I spend a few hours painting backgrounds and adding shading. She spends some time on text bubbles and formatting..
Really it just takes forever, but at least its not all those hours for just one person!