Probably just simply the desire to illustrate importance with no actual market in mind. But perhaps still grounded a bit on knowledge of transactions in an act

Probably just simply the desire to illustrate importance with no actual market in mind. But perhaps still grounded a bit on knowledge of transactions in an actual manuscript collector's scene market. That, from my point of view, may or may not exist. If it does exist it's unlikely to have transactions of that size, but it would also only transact comparatively minor manuscripts. And multiplying up minor transaction volumes to enormous valuations isn't exactly unheard of. The only difference is that the factor derived from "importance" is a bit subjective, but that's the nature of a collector's market and the claim isn't really stating anything like precision. It's not like the library could have taken up a mortgage with the manuscripts as security.