About the next layout--I think I could cut even more by taking the text down a point in size. I don't want to get too aggressive about that, because obviously teeny text is hard to read, but I do think the print is pretty big right now. There's a weird multiplier effect because the shorter the book is, the smaller you can make the side margins (the binding will swallow up words in a thicker book), which of course makes the book smaller still.
The publishing-on-demand service I use is called CreateSpace and is owned by Amazon.com. They basically offer three distribution channels: The CreateSpace store (ever heard of that?), Amazon.com (now, that you've heard of), and something called Expanded Distribution (libraries and independent bookstores).
The weird thing is, you have to set a single list price (i.e. the price a reader will pay), but the amount you make depends on the distribution channel. For example, you could set a price of $20 for your 550-page book, and you would make $3.50 on every copy sold through the CreateSpace store (ooh! more than 15%) and lose 50 cents on every copy sold through Amazon.com (oops). Not that they'll let you sell your books at a loss, of course, but even if you were dim enough to do this, you'd probably go under posthaste because many more people buy through Amazon.com than the CreateSpace store.
The most expensive option for the author is Expanded Distribution. In order to use Expanded Distribution at all, you have to pony up $40, which also makes the book cheaper for the author, regardless of distribution channel. So unless CreateSpace makes a perfectly ghastly product, I'll pony up right away, which will bring the cost down, but not enough for me to use Expanded Distribution. Then I'll lay it out again (notice that I'm not making weeping noises--I have been shamed by Jeremy Robinson's example), put it on Expanded Distribution, and if I do a really good job, maybe drop the price by a buck or two for everyone!
(In defense of my crying and moaning about layout: I have to say that it (like all visual arts) is not something that comes naturally to me. I think I've made a decent-looking layout, but I feel like I have no instinctual understanding of how moving X will affect Y and Z--I just have to do it, see what happens, go back and fix what that screwed up, etc. You know how a really good hairdresser can just cut wet hair so that it looks great dry, even though wet hair is longer and a different texture than dry hair? I really, really lack that gift.)