Yo' mama.
Books on electronics, even analogue, have a much bigger potential market than optics books. So far I've sold about one copy for every 3 members of the Optical Society, but that's still only about 6000 copies. Getting the same market penetration in the IEEE would be about 140,000 copies.
You have to amortize the cost over significantly smaller print runs. Besides, mine's over 800 pages of small print!
Cheers
Phil Hobbs