You really have to separate them out. The reason for such large swings is the availability of funding.
For instance, at my local government funded kill shelter, I can adopt a dog for $80. The director of the shelter is a vet, and all vetting is done on the premises. The employees are paid with my tax dollars. The facility was built with my tax dollars. They don't socialize the dogs, they don't wash them, and they don't do anything to train them while they are there. They can afford to be cheap.
The local no-kill shelter, which was built with donation funding (this took many years to raise), operates with all volunteers running it, including the front desk, the kennel area, etc, has to use a regular vet, and pay the taxes and mortgage on their building, along with all their utilities, from donation funding. Just imagine their monthly cost of operation!
My rescue group is ALL volunteer, and funded by ALL donation. We have no money to build a shelter, use volunteer foster homes for dogs, (who pay for all food and treats themselves), and have to use regular vets at FULL price (unless they give us a discount), to vet all of our animals. We pay for training, and any large medical bills for our dogs, out of donations and adoption fees from other dogs.
My local shelter? $80 to adopt anything.
My local no-kill shelter? $300 for an adult dog, $450 for a puppy.
My rescue group? $300 to adopt anything.
I consider ALL of those fees to be reasonable.
Have worked in rescue a long time.