It's pretty standard in academic publishing. The author is possibly not
getting paid by the publisher much if at all to write it (they're employed
as an academic and research/writing is what they do in between teaching and
admin), but the cover price basically covers the publisher's costs in terms
of editing, typesetting, any promotion etc.
They know they will sell at least X library copies and that's enough to
recoup their costs. Any others are a bonus. The libraries will buy the
hardback, and they might get a deal where they get electronic access as
well.
Printing costs are minimal compared with their overheads and there's no
reason to offer a cheaper way to get the book, since that will mean they
don't recoup their expenses from the libraries.
So, if you want to read it, wait a few months and then see if you can get it
from your library on inter-library loan.
Theo