I thought I should also add that Bruce Dundee Plank is not beveled on the ends and I have had some very bad end matches which require a lot of effort sorting to prevent bumps.

I would guess the builder steers everyone to pre-finished so that he doesn't have another trade vying for time and space in the house. Pre-finished is one time install then cover up the floors to protect them, versus multiple visits to sand and apply coats of finish for site finishing.

Floorguy -
Box stores do not install site finished wood.

I was stating box stores charge 4.50 a sq ft for install alone plus the wood. Thats how i got 8 - 9 bucks.

The 2 bucks a square install i was referring to the avg price for site finished wood. I dont know why there is this difference, but there is.

Prefinished costs more than site-finished to install because you have to be so delicate with it. You can bang and man-handle (or wood-handle) unfinished when installing it because you can always fix your mistakes when you sand it.

I charge 50-100% more to install prefinished. I charge even more when it's a glue down.

Imo using pre-finished is an acceptable choice on either new work or occupied.

There is one main issue you need to keep front and center. The installer is either going to give you a ho-hum looking job... or a spectacular job. Regardless of what material it is, pre-finished takes more patience and skill imo. Quite often the labor charge is more than the material cost.