Don't know about the value.
As far as a sub and its stays in a corner it should be pretty good. it uses the walls to extend the mouth. It supposedly goes as low as the full size because of its location. It drops off rapidly after 35 Hz like the full size. I built one as a sub and it was parked under my workbench on its side which further extended the mouth and I really liked it. It did take up too much room so it got removed and does not work well outside its element.
It seemed to go lower by my perception. it made the wall creak in my garage when I cranked it.