If you take good care of your chameleon there will be no need for a vet visit. I've been keeping reptiles/amphibians for about 15 years and I've never had to take any to the vet, and not because I don't want to, but because I've just never had to.
Proper lighting, supplementing, food variety, hydration/water quality, and cage layout will ensure a happy, healthy cham.
To answer your question though, x-rays are roughly 50$, fecals are roughly 25$, and I think that's all you'd get. That's on the low end. Some vets charge double, triple, and quadruple that so it is hard to give a true estimate.
As a preventative measure for parasites (almost all captive reptiles will have parasites, despite people's best efforts to keep their cages clean....crickets often have pinworms) you can use a WEAK dose of Panacur/fenbendazol once every 6-8 months. It is safe and will keep your chameleon free of parasites.