Profit isn't revenue, for one thing. Does that hypothetical $50k/month treatment cost $49,999/month to manufacture? That's the story for a lot of drugs.
Whether or not the unit economics are $49,999/month or $49/month has no bearing on this. Treatments aren't commodities, they aren't apples at the grocer, where if the prices are too high, you just go to a competitor across the street.
Maybe Monsanto, Toll Brothers, and local governments should be funding cancer research?
More importantly, every major pharma has a compassionate use program that helps people who can't afford the drugs get them, through offsets and credits. I understand the desire to make pharma look like pure-evil profit mongers, but the reality is that this is not an easy business to be in.
It's pretty widely accepted the presence of this government-enforced monopoly significantly increases the price of many drugs.
The standard argument in favor of this is that it incentivizes R&D and we wouldn't have these drugs otherwise. I think it's debatable either way, but claiming these companies don't take advantage of this arrangement to increase prices is not true.
There is nothing wrong with patents "promoting the Arts and Sciences".
The problem in the US is that your largest buyers (Medicare, Medicaid, VA, Tricare) aren't allowed to properly use their buying power to push pharma companies on prices.
At the same time, there's very little restriction on pharma companies advertising directly to patients (banned in most nations) which puts pressure on GPs and specialists to over/off-label prescribe unnecessary pharma.
Prices in most countries are cheaper than the US because of that buying power that the government has, along with independent assessment of the value of new drugs and treatments in terms of QALY and cost/benefit to the people.
I work for a US biotech that is wholly owned by a EU pharma, not the US.