Most of this stuff is marked up way too much and most of the time you can buy something similar from Swansons. I bought Carlsons cod liver oil 16 ounces for something like $23.28 which costs $50 at any health food store.
Some of the more complicated Swanson formulas would be the ones I suspect might be inferior though.
If your buying some simple herb like Hawthorne Berry for example I don't see how you could go wrong.
You could go to this site and buy quality herbs by the pound and then put them in capsules yourself. I figure this is what Swansons is doing.