Agreed - I’ve ended up installing 4 (inspected) ones over the years myself, and one I paid an electrician for (they also had to upgrade the main service feed).
IMO, what usually drives up the price is the ancillary stuff - opening up a wall (and re-finishing it) because there isn’t enough physical space, or adding extra main panel capacity/service capacity because the main feed is insufficient, or having to run heavier than expected wiring because the only available space gets really hot (poorly ventilated attic space), or having to run surface conduit due to a specific challenge with framing.
Then add in labor (where I was in a high cost of labor area), and it can get expensive quick.
An actual surface mount subpanel and appropriate wires/breakers is usually only a couple hundred bucks total like you note.
IMO, what usually drives up the price is the ancillary stuff - opening up a wall (and re-finishing it) because there isn’t enough physical space, or adding extra main panel capacity/service capacity because the main feed is insufficient, or having to run heavier than expected wiring because the only available space gets really hot (poorly ventilated attic space), or having to run surface conduit due to a specific challenge with framing.
Then add in labor (where I was in a high cost of labor area), and it can get expensive quick.
An actual surface mount subpanel and appropriate wires/breakers is usually only a couple hundred bucks total like you note.