Well it depends on specifics.
Not every rescue can do everything mentioned as "good rescue". Some local SPCA do not want to work with reptiles or reptile rescues or rescues. Not all rescues have enough training to teach police or SPCA workers anything, much less give them classes or look reliable enough to be asked to do so.
Some good rescues(that aren't the Superb Rescues) still do good work, in taking in unwanted animals. I don't mind if they ALSO sell their own animals.. as long as all that is separate. I also don't mind there being a fee.... and I don't care what the fee is. Many dog shelters charge over a hundred dollars for a puppy... but it's not considered scamming to do so, since lots of the money gets put back into the shelter. Same with rescues. If you take in rescues, you WILL rack up a considerable amount of vet bills, sometimes on a single animal. Taking in donations means you MUST be registered legally... 501K status is a good reliable way to tell a Rescue that's really serious from someone who is just taking in animals and trying to 'save' them.
Hint: if they are a 501K, they have to provide their paperwork on request.
Lots of people may rescue rats for instance... and when they offer them for adoption, the fee will be WAY higher than you can go buy a rat(especailly at feeder prices), because they do want to ensure only a serious home considers their pets. They also rack up vet bills... all animal rescue tend to. So lots more than "market price" for a normal BP is not automatically a scam or a flipper.
The main thing to me
"Are the pets healthy that are offered for 'adoption'?"
"Are the people open about how the pets are kept, are they practicing quarentine?"
"Can they offer a vet that is their accreditted vet on file for their rescue animals' care?"
"If 501K claims(non-profit) will they offer their paperwork on request?"
Positive answers to those tell me how much I'll trust their operation or not.