There is a set of the order in the military museum in Taipei that has the blue enamel scattered all over the display. I am not sure if that is actually Chiang's or not as there are many items belonging to him that are displayed.
20k is still a lot of money for a vague letter. How I see it, the letter for the hat/epaulettes does say it was custom made and given by Madame Chiang with the President's blessing, but no proof if he actually wore it or even owned it.
I bought a presentation medal on auction that the auctioneer stated belonged to well known US general and the owner was going to get me a letter from the granddaughter stating this, nothing so far. Other than that, I only put the money on the medal and not the statement itself.