Investing in Lewis: Admiration Inflation?

The monetary value of C. S. Lewis books, especially first editions, keeps going up. For proof, check the latest catalog of Nigel Williams Rare Books, London.

First British edition of Out of the Silent Planet $47
First British edition of Perelandra – $542
First British edition of Miracles – $97
First British edition of The Silver Chair – $2748
First British edition of Surprised By Joy – $60
First British edition of The Last Battle – $1099
First British ediiton of Till We Have Faces – $149
First British edition of Letters to Malcolm – $31
First British edition of Narrative Poems – $75