I think they view the profit as their wages, also the "after taxes and expenses" comment, surely that includes fees?
having thought about this, my "man what does" charges 140 a day and does everything except plastering, brickwork and stuff that needs certification. So for that 9,000 you suggest, I could get 10 days work and 7000 quids worth of materials and stuff like skip hire. You'd get quite a lot done for that. This wouldn't be mates rates or trade prices, just what anyone would pay and I live in the south of the UK in an expensive area. The other thing to think about is that its not possible to tell the quality of things like bathrooms and kitchens on TV. What might look like a high end expensive suite might in fact be a budget one from B and Q.