A 10 minute video typically represents a few hours work (minimum).
Yup!
The likes of Afrotech mods videos take 30+ hours work for a 5 minute video.
John Simpson (the BBC reporter) had a rule of thumb that after shooting was completed, it took him 1 hour for him to prepare each 1 minute broadcast video.
It would be interesting to ask BigClive (unless he answered already) about his preparation time. Of course, many YouTubers do more polishing and preparation (that's why it would be interesting). Entertainment-wise, his videos are high quality.
One could create an "educational/explanatory" electronics channels with purely 3D animations (I'm sure those exist already). That would definitely take so much more time to prepare than the actual video length. Not just the modeling and animating part, but if you do high resolution and high quality physical material rendering (on not the highest end computers), it could take a day just to get a few frames rendered (or if you super optimize, you might get a frame in up to a few minutes). This would be really interesting to tackle, but requires far more knowledge than I posses. To explain something, you must first understand it really really well. EE students would probably be able to have a good enough level of understanding.