Zimhunter,
It is quite obvious that you have never regulated a double, all you did was tweek the loads on a couple of them to get the best results from two rifles that were already regulated by the factory.
Lets talk about the shotguns first. You claim that shotguns are regulated like double rifles, and to some degree you are correct. At the factory they set the barrels to superimpose two loads of shot, one over the other by making them converge and setting the muzzles at the same level while they are soldered together.
All the better made guns, and especially the better older guns, were set up to throw two patterns of shot to converge at a given distance. Light weight bird guns were most likely set to converge at 25 yards or so, and waterfowl guns were set to do the same at about 40 yards. They will still do that today, IF, you use shells of similar power and speed. If you have never patterned a shotgun that shot one barrel high and one low, then you have not done much work at the pattern board. I have shot many shotguns at a pattern board and have found a handfull that would not throw their patterns one over the other at any distance. In most cases these were the cheaper guns.
You are correct in saying that the cost of a good double is because they are difficult to get regulated, and to dispute that you offer up shotguns and Corvairs. I owned a Corvair motor one time, it was in a Harley trike frame. The motors were good enough, but only after you removed some of the Rube Goldburg cooling cowling. Much of the rest of the car was crap, and I never liked Ralph Nader either. He was a self promoting asshole!
Sabbati got in trouble, not because they made bad guns, but because they tried to fix the problem with a very crude way of altering the muzzles, then trying to pass them off as new and well regulated guns. Cabelas got into trouble along with them because they were not taking care of customers early on. They didn't really start to play fair till it was discovered and widely talked up, how widespread the problem really was.
To get back to your two doubles mentioned first, you said that they both shot within two inches at 50 yards. That's because they were well regulated to do so at the factory. You do not get the credit just because you tweaked the loads you shot in them. If you want to prove what a good regulator you really are, send me one of them and I will unsolder it for you and send it back. Then you can get some real firsthand experience in regulating a double. Till you have done at least one regulating job, please refrain from condemning those who have more experience at it than you do.