I suppose I can claim to have some knowledge of what's involved...!
It is, indeed, very time consuming if you do it the way I do, i.e. with lots of scene changes and closeups etc. If you are just filming a lecture, which is very well-suited to the way David Charlesworth works, for example, the editing is much simplified, as the scenes are much longer.
But if someone is going to do this for a living, they must attract HUGE sponsorship to pay for it. When I started, Festool, Woodford and JSP all supported me with stuff for the workshop. But I couldn't find anyone who would actually sponsor me financially. The costs, even on a shoestring like mine, are not trivial. In 4 years my sales have covered roughly half what I have actually spent and a quarter of that has been in the last three months, since launching WE 4 & 5.
I know the US is a bigger market but I bet it's not easy even there. Marc Spag seems to be succeeding, and very good luck to him. If I make another, it will not cost very much, as I already have the kit, but the first two were a different matter. I do it because I enjoy it and have the time to do it properly and if I thought I could make a living at it, I probably would. But anyone considering starting to podcast needs to be prepared to fund it for a very long time, I reckon, and be prepared never to get their money back, let alone make a profit.
Sorry to sound so negative, but that's the way I see it.
S