There aren't many remarkable qualities to the National Institute of Standards and Technology's jar of peanut butter (otherwise known as "Standard Reference Material 2387"). It's just a mix of the usual peanut butter suspects: peanuts, hydrogenated fat, sugar, and salt, but it's been pored over by scientists for more than a decade, and it's kinda the Platonic ideal of peanut butters. That's why it costs $761 for a jar.
The peanut butter, which was made by a company "whose name you would recognize" (according to scientist Katherine Sharpless, who works at the NIST), was made at the behest of the government for the sole purpose of its use in experiments using gas chromatographs, mass spectrometers, and other scientific gadgets whose names are increasingly obscure. Essentially, it stands as a paragon of what peanut butter should be, and is used as a reference by other companies and agencies that need a nice, stable peanut butter to sample.