Considering the James Van Der Beek of Dawson's Creek fame is having to hold a fundraising auction of his memorabilia to fund his cancer treatment, cancer is expensive in the US.
actually a difference is also how many players along the supply chain siphon money out of the process. the more greed is allowed and acted on for the treatment, the more expensive it gets. introduce layers of insurances, hedgefonds, pension funds, lobbyism, ... it adds up to riddiculous amounts far beyond the original R&D/infrastructure/treatment costs.
And also downsides, e.g. many treatments just aren't available, and many others would never have had their discovery funded without the market-based system existing.
Governments can (and do) directly fund medical research including drug discovery. This is in part because governments of even just middling competence have an incentive to keep their workforce (which also includes their military) healthy.
It's a lot more expensive in the US. Three years of ribociclib is US$100k here in Argentina, which dwarfs the usual costs of things like chemotherapy, radiation therapy, and surgical resection. (All of which is normally paid for either by a health plan or by the public hospital system.) In the US, if you have to go through all of that, I think the cost is going to be at least an order of magnitude higher.