Hamsters are considered 'exotic' in terms of veterinary medicine. Based on my experience with exotic vets, the office visit alone can be around $50-60.
To treat wet tail, the vet will prescribe antibiotics. So lets say $10-15.
They may prescribe anti-diarrheal medications or fluids as well. That may be another few dollars each.
Meds in general aren't expensive. It's the office visit and tests that are expensive.