I see what you are saying factor 30 but I have a relative who a self employed carpenter.
People forget they have to pay to run / replace a van, pay for all of their own pension, public liability insurance, tools, tax and a lot of work goes on which people do not see like he has to visit suppliers to get the best material for the job.
Often the job is some distance away from home eg he is now working on a kitchen 60 miles from home ( today ).
It is an easy journey as it is near the motorway both ends.
He did 1 job 200 miles away. He fitted a kitchen for some people in their old house and they were very satisfied with it.
He did point out that it was going to be expensive for him to work on the new house as he had to factor in Bed and Breakfast etc but they still wanted him to do the job even though they could have got somebody cheaper locally.
Sometimes he even goes into places when he is on holiday to keep up to date.
His wife takes phone calls etc at home as well as doing the accounts / tax returns etc and I helped 3 times on this side when she was in hospital.