So it's ethical to overcharge for a lamp, but unethical to overcharge for healthcare?
What is your definition of over charging?
Buyers don't buy based on price alone. You need to take trust, after sales service into account.
Let me rephrase the question. Is it ethical to overcharge for a lamp, but unethical to overcharge for healthcare?
No. Why do you differentiate between types of products and services? In the free market, you offer something for a price, and there is no unethical price. In the non-free market, the question doesn't even need an answer, because it is not you the customer, or you the merchant, or you the doctor who decides. It is the one dominating over you, based on his physical power to harm you.
So how will you know if you are really about to die or the doctor just needs to make a yacht payment?