There is zero chance it costs $5 per dose because blinatumomab is a bi-specific T cell engager which is a monoclonal antibody made by extracting it from a cloned white blood cell created from recombinant DNA. The yield for this process is extremely low and it's really complicated in the best of times. The cost of the pipette tips and other consumables used by the lab automation alone probably costs more.

The flip side is that it treats a rare form of leukemia so the market isn't very big and since they can't lower the price enough to compete with chemo, they have to actually charge more to get their money back. For example chemo might cost $10k, but their drug costs $10k to make per person so if they charged $50k they might not even get enough customers to break even. So instead they charge $200k to get the most from the patients they can capture like the X% of patients who are allergic to the chemo drugs and have no choice (Just an example, I don't know the specifics for blinatumomab)