Where would you put TriStar/Armsan in that mix?
(For the record I have multiple Model-12s, ditto Rem 1100s and 870s (Express & Wing), an early Miroku/Browning Citori, another Finnish "Lion" O/U, more Ithaca-37s, a couple of Berettas (Pigeon & 6xx)...
...and a little
Tristar Viper at the tail-end of that list that..... "ain't bad" )
https://tsswarehouse.com/wp-content/uploads/imp/3/5/4/6/0/6/354606.jpg
(for less than $500, in fact, it's incredible)
As I pointed out earlier, most of the Turkish semis are great guns for the money, the viper is a good solid value; I bought one for the 4-H Trap program, in 20 ga. for the kids who's dad would send them out with a 30" barreled, 14.5 LOP 1100 when they were 10 years old, to use. They tended to shoot the Tri-Star 20 better, and when I tried it out, it busted clays just fine, and it being an a300 clone, easy to take care of.
But the TT-15 Trap gun (O/U, top single, or under single) is not capable of holding up to the volume of rounds beyond what all but the most casual trapshooter puts through their gun. The other main problem is that while the have most of the bells and whistles a Trap gun should have, they lack an important fit component for Trap: a parallel comb. Though the comb on most TT-15 versions is adjustable, it has way too much drop for that feature to be useful; it just raises the cheek up so the gun can slap it higher up.
While George P. is right, Purdey & etc. owners are dilegent in sending their treasures in to have loving care lavished upon them (as well they should) ; the guns themselves do stand up to higher volumes of shells than a TT-15 would, just because of attention to detail-using the best quality parts, the best steels for recievers and barrels, etc. They don't have a price point to stick with.
It comes down to quality costs money. Turkish manufacturers are well capable of putting out excellent quality guns, and some are made. But the vast majority of Turkish gun production is in the Sears catalog of c. 1900 "Aubrey" brand shotguns level of quality. Those were made for sears by (usually) Belgian manufacturers to match a price point set by Sears, though with much better steel and fluid steel barrels instead of laminated twist or Damascus twist. This is by design. Get your name out there, sell some volume, then you can get the quality going up with time, as they learn as did the Belgian shops did in the latter 19th and early 20 century did.
There will always be sombody willing to build guns at a lower price point to get a share of the market. Taurus and Armscor are two more recent examples; the former having several ups and downs in the market, reflecting different ownerships' visions for the brand. Armscor guns started out with a sketchy reputation, and have developed into an excellent brand for the money. Their investment in .22 TCM and making 1911 platform guns in many different calibers and configurations shows they keep going upward and onward.