That's a really good price on an Express. If it had an aluminum trigger plate (push up the lifter while looking down the bottom of the gun, toward the front of the trigger plate inside the receiver- if you see two little whitish rectangles, it's aluminum), an old style safety (the nonlocking kind, as far as I know none with aluminum trigger plates had locking safeties) and no dimples on the magazine tube, I would be absolutely forced to adopt it and bring it home so it could have a good home with its sister Cinderella 870s.
Even if it is a newer version with dimples and a plastic trigger plate, that is a good price. All that can be fixed, and the plastic trigger plates in truth seem to hold up just as well. It's just that I am an old fuddyduddy and lazy to boot.
BTW, I think you are talking about seeing the heads of the rivets holding in the ejector, not pins. There are two pins holding in the trigger plate, they are close to the bottom of the receiver and are visible on both sides. The ejector rivets are on the left side toward the top of the receiver. Sometimes they are left protruding a bit during finishing and wear a bit faster, thus becoming more visible than ordinarily is the case. Finish wear on well used Expresses is a given, but they can be phosphate finished and hold up quite well.
That seems a good price on the Model 12 too, by local standards. If it were a good tight take-down model with a 2 3/4" chamber, it might get to join the collection here too.
lpl/nc