A huge, huge, cost driver in many of the applications is the fact that they have to integrate with the old systems in numerous ways.
A startup could probably build the basic version of many of these apps no problem, but that's only the tip of the iceberg. When you have to then import millions of customer records, which were not stored in any particular format (they're idiosyncratic with each doctor/office), and then integrate with the COBOL based system vendor 1 uses, and the IBM Mainframe that vendor 2 uses, oh, and those systems were never intended to interconnect with anything and the vendors are years behind schedule as well, and all while you have lawyers breathing down your neck with a 28 inch thick binder with all of the regulations you need to follow written in impenetrable legalese you can see how it can cost billions of dollars.
Your startup guys heads would explode if you asked them to write a formal specification for an interconnection system between their elegant web frameworks and a big blob binary COBOL based record system on an IBM 360 with only hardcopy documentation written by a vendor that went out of business in the 80s. And yes, healthcare systems still run in environments like that for the reasons mentioned above: making a new system is too hard/expensive.
Oh, and the vendor that had the lowest bid for the contract is planning to outsource to some country that doesn't speak English and is 12 hours offset from your local time.
