Roughly 25 years ago, I did work on a system that went to a major drug company. I learned that at that time, it cost roughly $1 billion to get a new drug to market. Of the hundreds of candidates that they would start testing, only 1 or 2 would have the right properties of not killing the patient, not having horrible side effects, etc. And the documentation required by the regulators would fill several semis, because it isn't enough to prove to yourselves that you have a wonder drug, you must prove it to the regulators. This is to prevent Joe's Bait and Pharmacology Shop from putting snake oil on the market. Once on the market, your drug must compete against others. And if those others are in their generic phase, you can express pricing pressure as well.
Then the market for the drug must be assessed. In the case of antibiotics, there are many of them out there, many in generics, so bringing a new one on the market is destined to not sell well...at least as long as too many people aren't dying from super-bugs.
This is a prime area for government research and development. The conservatives and libertarians will whine about the fed. gov. getting into the drug business. However, this is what we expect our government to do, i.e., make up for the shortfalls of private industry. The way I look at it, private industry has a big tote board. When frequency of deaths due to super-bugs rise above a certain level, they'll move. Until then, the conservatives and libertarians will gladly attend your funeral...just kidding, they don't give a flying rat's ass about you.