The bag costs the end user $800, mostly because of govern-cement regulations.
Also due to the way insurance works. (again, because of govern-cement regulations)
Add to that the malpractice insurance (again, because govern-cement got in the way of doing things in an appropriate way)
And, there is the costs involved in actually producing extremely pure water and salt, packing and shipping it with no chance of contamination.

It isn't that hard to produce ultra pure water, just have to have an air tight completely sterile processing plant.
Ever wash salt?

Now enter the govern-cement. The amount of regulations requires a full time, very expensive, chemical engineer to administer the regulations. Then add a few secretaries to process the regulations and one lawyer to put their stamp of approval that the regulations were read properly. And none of this make the process any better. None of these people are actually involved in quality control.

Half of your hospital bill is malpractice insurance. This is caused by the way the lawyers (those who tell the govern-cement how to do) have made the legal system. Court cases are soooo costly that settling out of court for hundreds of thousands is cheaper. And those million dollar settlements are only the tip of the iceberg of what it actually costs. Just think, if we had a doctor system where it was, if we break it, we will do our best to fix it. Medicine is practice. There is no monetary value that will make it avoid incidence nor is money a replacement for life.

Then there is the poor hospitals. Say the saline actually cost $400, but you know, from experience, the insurance company will under pay you. So, you tell the insurance company it cost $800, so that you may in fact get your $400. This entire process is wrong, but it is the result of regulations. If the insurance industry was actually held to real standards, then these shenanigans would never be allowed to happen. But, now, these shenanigans are codified.

And last, hospitals cannot be built too close to each other. Because of govern-cement regulations. Thus, you have an area that really needs three hospitals. Well, it has to do with the one. And thus, there is no real competition, and certain hospitals are so busy, that even with a life threatening, minutes to live situation you are still waiting for hours in the emergency receiving room.