[lamington]

This is a combination of the economics of publishing, plus a degree of prestige.

Books are very expensive in small print runs (and all the Adria/El Bulli books are small runs), and the production values of these books are very high -- the artwork is generally very good, the photography too. These are high quality books, and as such probably need to be regarded as something other than a mere book about food (and they definitely aren't cookbooks in any conventional sense) -- that doesn't mean I think it's necessary for books like this to exist!

I have two inordinately expensive food books: Los Postres de El Bulli (Albert Adria), and Dessert Cuisine (Oriol Balaguer). They both cost in the order of US$130. OUCH. But they are very special and convey knowledge and ideas which I couldn't have found elsewhere.

Academic books which aren't going to be bought in their 1000s by students frequently exceed $100 by a considerable amount, and there isn't any prestige-premium (or superfancy colour photography) involved there, I assure you!