No matter how much is "written off" (and it is extreme, isn't it?), the Catch-22 is that if you don't have insurance you get to pay the full list price. The price only gets reduced to the "contracted amount" for those who DO have insurance. It's a very strange system.
And, you can think it is good or think it is bad, but the extension of parents' benefits until age 27 was done with some reasoning behind it:
1. It may not have been true with your daughter, but many college careers these days extend well past the age of 21. Five years or a little more is now "normal" for undergraduates (don't ask me why), and for some there is grad school after that.
2. It is our young folks coming into the workforce that in general are having a very tough time finding jobs--and especially finding jobs at the level that matches their newly-minted academic credentials. Not finding a good job combined with the necessity of beginning to pay off those excruciating student loans can create a very tough squeeze on this age group. Being able to keep them on their parents' insurance for a few years gives them a little room to breathe, and isn't really a huge cost factor because as a group folks this age represent a low risk for health insurers. Plus, this coverage isn't free; there's still a premium to pay. Whether the family does it or the employer does it just depends on what kind of deal you have at work.
Like I said, you can agree or not with the reasoning, but at least there was some.