This is exactly why when we have done rescue we charge $, usually around what an accident/injury would cost to treat at a reasonable vet. So in early 90s I charged around $100. We don't have a set-up currently appropriate for rescue (aside from any of our own breed) so don't do it currently, but if did right now, we'd probably charge around $175. Aside from checking references and their vet i feel like this shows that they can come up with that $ when they want to.
Still a bargain as I always correct behavior issues that may have gotten the dog dumped, get them spayed/neutered, obedience and manners train them up through a CGC. they were all microchipped, and fully vetted up.
~ Tracy