I've just finished a mega painting job. (And yes the client loved it. Thanks for asking.) Even I was surprised at how long the prep work took. (Prep. work is all the filling, sanding, vacuuming, washing, sweeping, and undercoating work that all paint jobs need.)
Like all nerds, I had recorded my time. Then being a visual person, I made a pie chart. NOW I could see what was going on!
I was surprised to see that the prep and painting of the TRIM had taken 50% of my total time. Trim includes doors and frames, windows, skirting boards and in this case, picture rails: in short, the Timber bits. And every piece of timber was detailed and fancy.
So, if you have a neat old house with all the decorative trim (even though the trim's surface area is small), prep. and painting the trim could cost as much as all the walls and ceilings combined.
I've been drawing and painting since I was a kid. I've studied art and design and have worked in visual areas my whole life. Now I'm a house painter!