Good question, infact it's a question that I run into and may be
publishing on the site.

There are a few reasons why there is a fee for this competition, I will
get to that as soon as I get the later part of your question out of the
way.

The book is being self-published, which means that all expenses are on
us. The book will then be priced to cover the costs.

As for the contest fee, at the start of this competition, submissions
were free, however after receiving 100's of photographs that simply
have nothing to do with the theme, some without extensions or
information, we decided to add a small fee, this way only people that
are serious and only those who are truly interested will submit
entries.
This idea was infact forwarded to me by a forum member who also
occasionaly runs contests.

Also once this contest is over, all money generated from it will be
donated.
Prizes for this contests are also on us.

Thanks for asking the question, if you have anymore, feel free... and
if you would like to participate, please do so...