The only bird flippers that are in my area that I'm aware of aren't what I would call bird flippers. I think most are bird rehabers. Kind of like house flippers. They buy a house that is usually in fairly poor shape then go in and rehab it, turn it into a really nice house and then turn around and sell it for a very good profit.
The flippers thaat I know willingly admit to being a bird flipper. They seek out those unwanted birds that have been cage bound for years that have been desocialized to the point that no one can handle them or someone who just hasn't spent much time with their bird so it's not as handleable as it once was. They offer a nominal fee and then once they have the bird, they start working with it and get it stick trained, step up trained and as social as they can within a relatively short period of time.
Is the bird a snuggle bug, nooooo, is the bird truely HAND TAME most likely not. But it at least gets the bird back in a position where it can find a good home. So although there are some flippers out there that buy a bird and then immediately turn around and resell it, there are also flippers that spend the time to evaluate the bird and spend the time to get it to where it's managable again.
But then there are some birds that a flipper might get that really doesn't need that much adjusting so they will immediately flip the bird to re-coop their investment. I've seen the couple I know do this and thought wow what a shame for that bird. But then again I realize that they do strive to find them a good home and like to deliver the bird to the prospective buyer to see how they will interact with the bird on their home turf and also it gives them a chance to do a low key home inspection.
I wouldn't hesitate to buy a bird from either one of them. I guess bird flippers serve some what of a purpose.
To me, flippers serve as much of a purpose as some of these Pet rescue centers that receive birds in for FREE or a small monetary donation, then quickly post them for adoption at an unrealistic price for a plucked bird with aggression issues as well as some other issues that they aren't even aware of. All the time gladly accepting donations from the general public.
OK, I'm off my soap box now.