An email to the editor of a book on innovations in IT education (who invited me to contribute an article on the philosophy of computer science):
I am a professor in a small university in a developing country, and after your kind invitation in November I asked you whether authors in developing countries can get a discount price when publishing in your book (originally US$110 per page.) You replied me that your organization may consider that in the future. Unfortunately I had to decline your invitation, because my university cannot afford to pay 1300US$ for my contribution to your book.
Concerning your kind review request for the very same book in this January: I am happy to review your chapter proposals at the cost of US$110 per page. As I work in a small university in a developing country, I may consider a lower price in the future.