I disagree.
Think of it this way. If it were truly laissez faire, then drug makers would charge a price high enough to still make it worthwhile. Unfortunately, the way antibiotics are paid for in US hospitals, the hospitals would lose money each time they used the drug.
Hell, we pay ~$80K to cure hepatitis C (millions have it in the US). If you have an antibiotic that cures a highly resistant infection that happens maybe a few hundred times in the US, why not charge something similar? What is the benefit to society to save someone's life?