Mostly not marketing (still large), but the R&D costs and clinical trial costs. The latter are in hundreds of millions to billions range for the entire journey from a promising discovery to an FDA-approved medicine.
e.g. is all the "discount coupon" pharmacy rigamarole considered marketing or administration.
[1] https://d18rn0p25nwr6d.cloudfront.net/CIK-0000078003/908eb6a...
Everybody else uses price controls to keep prices "reasonable"--the drug companies tolerate this so long as selling to the country exceeds their marginal cost of production. They count on the US market to recoup the $1B R&D costs.
Simply mandate that a drug company can't charge more in the US than they do in any other first world country. Major earthquake in drug costs.
The "discount card" bit is basically a reduction in revenue, it's neither marketing nor administration.
In a sane world - or literally any other country - that $300-$500 million in annual lobbying would be the literal difference that makes medicine accessible for those who need it. Instead, it goes to expensive lunches.
The problem is proving your drugs work
It's very hard and expensive to do