"All the time I see racks full of single shot and double barrel shotguns. Some are pricey, but many are quite reasonable. What are some sleepers out there that are good shotguns, but may be not as well known and could still be had at a decent price?"
I bought a revelation 310 in .410 for 150. Thats a mossberg 500 and for around 275 I could have gotten it out the door at wally world. Of course I like my walnut better and to me the fact that in was sold by western auto stores, and that type of thing is an era gone by, makes it worth not 10 to 20% less but adds a coolness factor.
There is a guy selling a revelation in 12 guage on armslist locally for 175 and will probably go 150.
I traded into a series one 311c (stevens) at around 250 in 20 guage. Walnut no beachwood, and case hardened receiver. This is the same gun as the fox b. No not an a h but hey, say what you will. Just do it after you see it and shoot it. Good stuff.
Not a shot gun but if ya like rimfires look at the 511 and 5teens remington bolt action. Have yet to shoot one that wasn't accurate.
Will any of these gain lotsa value, probably not.
So many great and small budget choices. Life is good. One curmudgeon's perspective.