Gryphon:
The Scott-built Rodda I just acquired is around 110 years old and cost less than 1/2 the cheapest new SxS double (Baikal excluded!), yet it will do this at 55 yds:

First two shots overlapped, second 2 shots touching!

My Jeffery .400 puts every shot into 1 1/2 inches at 55 yds all day, with most into an inch. That's a 6-inch group at 200 yds easily, and with open sights remember.

The Wilkes-made Manton .470 I picked up a while back will do this at 55 yds:

To answer your question though, there are probably really good ones and not so good ones in any price bracket. If you hand-load, you can tweak the loads a lot to improve regulation, provided the barrel-groups are good.

Several of the cheaper new doubles are adjustable via a jack-screw or wedge between the barrels. Provided each barrel groups well, these should be the most accurate doubles possible, at least in theory!

The Krieghoff 9.3 belonging to my mate Bruce K_ would shoot extremely accurate groups if he'd only stop tinkering with it!