No idea where you're getting your info from, but this type of analysis is rarely done. It seems the OP is asking about a typical exam that looks for parasite eggs that can be done at the vet clinic in 10 minutes. The testing you're talking about sounds like something we'd do for an ongoing issue with a sick snake for which we can't find a cause for illness.Thats preparation, what follows is biochemical analysis, you search for chemical markers or for specific proteins, produced either by parasites themselves or by immune responses to the parasites. Often if they find something under the microscope or during preparation, they follow up with a biochemical test to confirm it and to make it a solid diagnosis.
Cost-wise, our clinic charges $15 for a float AND smear, in which we look for parasite eggs and giardia. The exam fee is usually what costs more, about $45 here, but in Indiana at least, it is required by law for the vet to examine an animal at least once a year before being able to prescribe any medication. It's referred to as a doctor-patient relationship.