The reality is that this is all solving a problem that people don’t have.
Forced air is a terrible way to heat a building yet thats how most homes are heated, and it is good enough for most people.
If you perfectly size a furnace for the coldest days of the year, it is now oversized for the other 90% of days.
The cheapest way is to install a multi stage heating/cooling system that works on first stage most of the time, and second when it needs to, like having 2 small furnaces. This passes the ‘good enough’ test for the vast majority of homeowners.
Come to your house to quote, and only land 1/4 quotes maybe.
Schedule the workers
Order the equipment.
Get an electrical permit.
Pay for the truck and all the tools.
Insurance for the company and trucks.
Advertising costs
Warranty and callbacks
I can assure you that this is not the get rich quick scheme you may think it is.