That $25 is the intial visit for the vet to take a look at it, not to do anything else, no ultrasounds, no blood tests, no xrays, no meds, nothing more than an opinion from a vet from a 1-4 minute look at the animal. Also exotics specialists usually charge more.
Blood tests cost about $45, xrays can cost $50-$100 each, ultrasounds can be far more, longer more detailed exams can cost 2-3 times that $25. If the animal possibly need antibiotics, or other meds you will look at about $15-$60 per med.
I recently can verify an expense just to diagnose a sick monitorlizard, nothing beyond that, it was a friend who had a 5.5ft albig male that got sick in the last month or 2, it was $450 for a full exam, work up on blood and bodily fluids, xrays, etc etc etc. This price was from a vet that charges $25 for a normal exam for a single reptile with nothing obviously wrong.