Buy used and save even more money. An older model Express gun (pre magazine tube dimples, pre plastic trigger plate) has the same internal components as a Wingmaster, just a cheaper bead blasted outside finish and cheaper wood furniture (birch vs. walnut, though one of the oldest Express guns here has matte finished factory walnut). If you know 870s well enough to pick out one that hasn't been butchered by a kitchen table gunsmith, there's no need to buy new where 870s are concerned.
Only Wingmasters have been around long enough for a few to actually be worn out from shooting, and they are pretty easy to spot. A good used Wingmaster is as much shotgun as anyone needs, and many come in priced hundreds less than new equivalents. There's no need to turn up your nose at a used gun, unless you have more attitude than you do money.
And while they are not as widely available as in years gone by, there are still LE trade-in 870s to be had, too. Thing is, a lot of departments are now refurbishing their 870s rather than selling them off or trading them in. There are some used 870Ps that turn up, as well as older Wingmaster marked Riot and Police guns. Many look rough externally but have barely been used, their mechanical components are still in great shape. They're worth looking for.
As for me, I've been shooting 870s for about 40 years, and have yet to buy my first new one. I still find too many good deals on used ones.