What they charge might be made up, but the costs of developing these drugs are astronomical. My wife is a cancer research scientist in immunotherapies and she can burn through tens of thousands of dollars in materials running a single experiment. And if she makes a mistake - the money is wasted!
For sure, I don't mean to suggest it's cheap research. But whether you charge a lot or nothing for the first few doses out of the lab, it seems like this won't really make a dent in the research cost. (I don't know if this $375,000 number is in that category, or not.)