value delivered is not always proportional to time spent working. it's like the proverb of the engineer who fixes the machine by whacking it with a hammer. $5 to hit it, $995 for knowing where to hit it.
even a "simple" home HVAC project can involve a bunch of different subcontractors that work for different companies, have different schedules, etc. without knowledge of the industry and the individuals involved, selecting and managing the subcontractors directly would be a nightmare for the average homeowner. the general contractor can earn most of their 30% cut just by knowing who to call in the first place and getting them to show up. when you find a good one, you really want to hold onto their number.
even a "simple" home HVAC project can involve a bunch of different subcontractors that work for different companies, have different schedules, etc. without knowledge of the industry and the individuals involved, selecting and managing the subcontractors directly would be a nightmare for the average homeowner. the general contractor can earn most of their 30% cut just by knowing who to call in the first place and getting them to show up. when you find a good one, you really want to hold onto their number.