No sorry. I was quoting the cost of the liner option. This figure was given in the link from post # 15.I'm quoting prices from a real plumber in Florida where the ground is made of sand. (Very easy to dig.) I said, "$20 per foot". I don't know where you got $125 per foot. Maybe that's about cutting out the concrete?
Rent a gasoline powered concrete saw.
Funny, I own a saw like the one pictured in your post. I used it to build a utility room addition off to the side of my brick home. Also to open a crawl space in one of my rentals.