"But a Doctor can treat someone for AIDS, or some other incurable disease, and charge them handsomely for their services and potions with the sure knowledge that the patient is not going to be cured. "

I agree, Bert, and I know many doctors who are real merchants, however, the difference is that the Doctor will always give you the truth first, and then the recipe. If s/he does not, there are laws to put him in jail.:)

Un abrazo - Andrés