Thats because you don’t know the secret fairy places to look for the books!
Here are my favorite places to get affordable faery tradition books:
Books by RJ Stewart, Anastacia Nutt, Gareth Knight, Orion Foxwood and more:www.rjstewart.net
Gemma Gary and the Cornish Pellar Witches: http://troybooks.co.uk/
The three Nigels (Pennick, Jackson and Pearson) British traditional fairy witchcraft: http://www.capallbann.co.uk/
http://www.abebooks.com often has better prices on out of print books—though the real classics like Katharine Brigg’s books are still very pricey. I got all my Fiona MacLeod and Rudyard Kipling faery tradition books from abebooks at very good prices even some first editions.
And yes of course, for many things I still use Amazon. Be sure to check out to see if the really old books are available to read online for free, www.archive.org,www.gutenberg.org, www.sacred-texts.org are all very good sites with many books that amazon would charge you to read for free.