Out of 275 total hubs, 16 are yet to be published. Some await research, some await the inspiration to return, and others await photo opportunities or videos to be created.
Of my 259 published hubs, I'd say, on average, I spend about 4 hours start to finish, including formatting. Some have taken considerably longer; others less.
That's the problem with averaging things--the minute you toss in a small number, it drags the entire total down with it, making your score look less impressive if you're talking scores, or making your writing efforts look unimpressive or lazy.
It really depends upon the topic, and whether or not it is something I already know quite a bit about, or whether I need to do research.