Genuinely, it depends on my mood a lot, which is frustrating. But I can take anywhere from start to finish 6 hours for about 5 panels in a page, and other times, it takes me like 15 hours. haha. I can tell you on average it takes about 10 hours from start to finish.
But I feel like it's important for you to notice how much detail and effort you're putting into a piece. Personally, I put way more time and effort into something that's not specifically a comic page, but more like a stand alone piece. This pic below is fairly simple in concept, but I took a lot of extra time with the angles, hands, detail work, and coloring. This piece took about 3 hours.
(They get cut off, click to see full images)
Meanwhile, this whole set of pages including backgrounds and stuff took about 6 hours, which is double the time, but also more than 3 times as much stuff on the page. Basically, I put less details in comic pages and care way less about things being perfect, I just need it to be done.