You're a far better clays shooter than me, but I have to ask why you'd draw this line. My $400 Russian O/U has thrown thousands of pounds of lead down range and shows no signs of fatigue. It is truly an instrument of the "Brave, not the arrow." I can have a good day and break a bunch, or I can get distracted and forget everything I know and shoot like crap. Never have I had even the slightest thought that the gun held me back.
I don't mean to be argumentative--I'm just looking out for the budget-conscious/restricted who wants to play with guns sometimes. While I don't shoot a consistent 100 shells per month, there are seasons where I'll achieve that for a while. Then it drops off to 0 shells a month!
Hey, fair questions. The simple answer is that the vast majority of persons I have seen purchase O/U's under the $1,500 mark become dissatisfied. Generally, persons who are buying O/U's in this price range are just getting started in clay target sports, or they are very recreational shooter. If they become more serious about the clay target sports they generally change guns, lose money, and have established bad habits as they had to fit themselves to the gun vs fitting the gun to their body. The longer answer:
Acknowledging everything below is a generality and some persons do find a relatively inexpensive gun that does fit/seems to hold up:
Why not buy a cheaper O/U?:
1) Lack of stock adjustability: Unless you have the exact body type the manufacture had in mind while building the gun, they tend not to fit (yes, even which an adjustable comb). There is a lot more to gun fit than where your face touches the stock. To shoot and O/U more than 100 targets in a month, you are going to want the gun to fit, for reasons of recoil and good fundamentals.
2) Balance: most cheaper O/U's are quite barrel heavy or are light weight guns. Both are, in my opinion, negatives in shooting well.
3) Most (not all) don't hold up. I've had the privilege of coaching/teaching many people how to shoot clay target sports, and for most of those shooters who purchased a cheaper O/U regret it. Yes, I have watched $10k+ guns have significant mechanical issues. None-the-less the cheaper guns tend to have more trigger issues, firing pin issues, and generally longevity issues.
Why buy an auto?:
1) In the price range under $1,500 you are getting way more for you dollar when you purchase a quality auto (unless you find a heck of a deal, obviously). Shim kit to adjust fit, auto's are easier to learn, auto's are easier to correct when you make bad moves, recoil tends to be less, less thinking about chokes, less fatigue in not having to open and close the gun, etc.....
2) All the reasons I commonly hear that are negatives about Auto's are practically garbage: 1) they are less reliable (not if you buy a Beretta), 2) the top shooters shoot O/U's (almost all of the top shooters learned on Beretta autos, and likely the best shooter in the world right now Joseph Fanizzi, shoots a Beretta Auto), I hate picking up hulls (picking up hulls with a Mojo stick is way easier than opening and closing an O/U 50x), 3) I like different chokes (your choke isn't the problem...BTW most of the top shooters who do shoot O/U's have the same choke in both barrels), they are more difficult to clean (Well....maybe, but stripping a Beretta Auto and going to town with a can of carburetor cleaner really isn't that difficult).
So yes, I do not recommend lower end O/U's