First the paper mis-quoted the insured value, it's $312,500, and car has independent 3rd party appraisal of $300,000, trust me there were a lot of eyes and experts involved in this process. The insurance company is world class - American Collectors Insurance.
I respect everyone's opinion, I'd just add two things, just why should any rare & unique 1 of 1 Buick command big dollars and parity respect as a Camaro Copo, Hemi, or Corvette. Secondly, the insurance company recognizes several critical factors; first and foremost the Provenance & unique history of this car, and the Buick - Cadillac 4th Generation family who convince Billy Mitchell to build it this way - "pre-production", in simple terms it a white unicorn, there will only ever be one. Lastly, the fit & finish - show record of this particular Buick. This 65 RivGS has won just about every top National Award across North America (US & Canada) including "7" Best of Show awards for the entire field of American cars, It is the first Post WWII car to earn the timeless Elegance Award, and Essence of Design at two major concours shows.
In the end the insurance evaluation has little meaning to me at the owner other then risk mitigation/catastrophic loss, what I value most of all is finding, restoring to a coachwork standard that sets bar high, sharing the legacy & history of a very cool GM - Buick Story. It also brings quite a big smile to my face and cast of Buick owners when we earn recognition ahead of every other iconic GM, Dodge, etc...car ever build, on any given show day.
Best Col Andy