If every supplier in a market has the same overhead, it will pass through to customers, because suppliers cannot compete to eliminate it.

See also: high prices in destination shopping. The landlord sets the rent and all stores have to pay the rent, so all stores will have the same high prices no matter how stiff the competition between them.

But the high debt is why they want to command a high fee, not why they are able to.

They’re able to due to restricted supply.

Yes, it is due to restricted supply. But the reason why restricted supply exists, is partially because of the high debt.

Or perfectly inelastic demand. No one weighs the costs of life or death

The way I understood it, prospective doctors are only tolerating huge college debt because they will be highly paid and be able to pay back huge college debt. If fees goes down, people will simply avoid being doctors and study something else which is cheaper or a profession which command higher fees.

I don’t understand that - people won’t want to study medicine if tuition fees are reduced?

If doctor fees are reduced.

Medical schools charge students a lot because doctors get paid a lot, and doctors have to be getting paid a lot to justify the enormous debts medical schools leave them with. It's a vicious circle that will never end without serious government intervention.