[herr_oberst]

I was involved in general printing and layout for about 40 years, don't know much about book publishing.
A couple of questions.
Who owns the electronic files? You own the intellectual rights, thats a given, but if you have a run of 2500 and it's a huge hit and you need 10,000 more, will you be able to hand the printer your flash drive with all the digital layout and images and have them print more, or will you be renting the rights to the digital layout from the initial publisher?

Have you gone to more than one publisher to get a bid? Just because you went to a christian publisher, don't assume that they are going to be giving you the best deal. Lots of book publishers out there. Lots of really, really big printer houses that can gang stuff up and save you money.

Has the publisher offered different costs using different grades of materials and numbers of colors?

Is the 17.50 cost for 4/color perfectbound with superglossy paper throughout with a 6 color and 2 varnish boardstock cover, or is it just a work and tumble saddle stich self-cover on low grade paper?

You need to sit down with a sales rep that can walk you through your first printing job, someone you trust to tell you the answers, and give you options for every single step of the way.

Printing is not cheap, especially for the first timer. Like you said, you don't want to wind up with a bunch of never to be sold books in your garage while your 911 sits in your driveway.

Edit. A great source of graphic design and layout is the local college where you might be able to find a design student willing to work for cheap to help design the book.