With the proliferation of good used Model 12's, $600 sounds high, but everything's gone up the past couple years so who knows.
I switched to a Model 12 in 2019. The first one (pictured), a 1959 model, was off Gunbroker, and the seller stressed all the bad things about it and none of the good things. The stock was speckled with blue paint, the mag tube was dented in a couple places and wouldn't load or feed shells, one of the mag tube cap screws was missing, the mag tube was put on 180 degrees off so it wouldn't lock into place and was held there by a heavy piece of wire (coathanger wire) twisted tight instead, the barrel had a small bulge about three inches back (I was going to cut it anyway, so no big deal), the slide handle retaining spring was missing (a totally unnecessary part for function), it was covered in light rust freckling, and the action was full of old dried grease making it stiff to operate. My winning bid was $116. I took it apart, cleaned it, cut the barrel, remounted the sight bead, turned out a plug to tap through the mag tube and work the dents out, found a screw in the parts bin for the end cap, and ordered the slide handle retaining spring from Numrich's, because why not? Anyway, all the work was pretty basic and only took a few hours. It's been my main match WB shotgun ever since.
I won another one later the same year, a 1937 model in excellent condition for $275 from GT Distributors, a police supplier in Austin, TX, that had "Bayside police" electric penciled on one side of the receiver, Bayside being a tiny community of less than 300 about 25 miles north of Corpus Christi. It had already been professionally cut down, so it was ready to go, and likely just rode around in the town's only police car for several years until it was disbanded and the shotgun ended up at the Austin store.