My almost ready kindle paperback is 132 pages. Printing costs for black ink on white paper would, I think, come to $2.43 (132x.012+.85). But there are 7 color images on 6 pages. Color costs are listed as .07 a page. Does that mean that my costs would be 126 pages at the .012 price plus 6 at 0.07 or does the .07 apply to all 132 pages, bringing the cost over $10?
The interior is either all b&w or all color. There is no middle ground. Were you using a regular offset printer and had signature binding, you could have an 8-page insert sewn in, but POD publishing doesn't work that way. If you don't want your book outrageously expensive, change your photos to grayscale. OTOH, if you think your readers will absorb the cost, go for it. But I'm thinking they probably won't.