On values:
I have a small collected library of books on the history of iconography. Most of it is Russian but I also have some references on Italian orthodoxy, which just barely predates the birth of the Renaissance.
Really good up-to-date resource books cost a fortune and have to be imported. Iconography is not well-appreciated in secular markets like North America. The research into older icons is difficult, since competing politics have over time effectively turned iconography into an illicit underground activity: for hundreds of years in some countries owning an icon could be a death sentence. Lay scholars of iconography don't receive compensation to cover the amount of investigation that needs to be done; generally the top researchers belong to the Church.
The books I have were mostly donated to me by my relatives who in turn bought them either from library sales or goodwill stores. The library sells them for a dollar apiece simply to avoid having to throw them away. The books from goodwill stores have inscriptions on the flyleaf such as "Happy Mother's Day, from your family 1985, We Love You."
At some point, these books would have set the purchaser back a fair sum. Given time and neglect on a bookshelf, they become worth less than the paper they were printed on. By luck or providence, a book or two finds its way to me. Honestly, I don't read them very much since the museum entries on icons are powerfully obscure and dry reading for the most part, or else wildly speculative to the point of describing the paranormal.
An entry on Cimabue, the great Italian master who pre-figured the Renaissance, gave me insight on how to finally render the wings on my icon of Gabriel. I am very far from mastering that technique, but at least I got through how to get feathers onto the wings. From Father Reynaldo SJ documenting countless dusty crawls through the sombre attics and cellars of ruined sanctuaries, to the publisher lavishly binding full colour images in heavy tomes that are presented to scholarly art department libraries around the world, to a bemused but reasonably devout housewife making ends meet through the Reagan/Gorbachev era, to the bottom of a millennial goodwill book bin, and then to me so I can figure out how to paint feathers, this book is the connection between my own work and that of the grand master employed in his sun-saturated Florentine workshop nearly eight hundred years ago.