Any 870 that hasn't been run over by a truck or used as an anchor is worth $150, DV.
And the thing about turnins is quite simple. Cruiser and tower guns get shot little but neglected and banged around much. Almost always they look like trash outside, but are near new inside.
Even if you get the dept trainer, 870s are so darn durable that it matters little.
One 870 at my old institution went on line for training in 1981. When I retired in 98 it was still the trainer, firing hundreds of rounds a month. Maintenance had been spotty. Total new parts, were new lumber.
Two here were agency weapons. My deer shooter started life as an Arlington Va, cruiser gun. Frankenstein, my overpublicized parts gun, has a receiver and some smaller parts that started off at the Md Pen.
I'd trust my life to either...