yikes it's hard to say. Like @AnnaLandin I do my pages in stages, not panel by panel. It really depends on how much detail I include as well. This page took me two weeks:

there are three panels, so if you average the time out, each panel took me about 4 hours. But in reality, that's not how much time I spent on each panel. There were a lot of details I had to move around on this page, so most of my time was spent in the initial thumbnailing/inking stage.
This page on the other hand took me about 6 hours total, which averages out to 1 hr per panel. In reality, some took longer, others were shorter.
honestly, I am pretty slow at creating art. I spend/waste a lot of time changing tiny details I'm not happy with, or staring at my reference pictures squeezing every last drop of inspiration out of them. Inking my pages takes the longest time, and is the most draining physically and emotionally. I enjoy coloring a lot more, and as you might expect, it goes much more quickly.