Photos and graphics can increase printing costs, especially if they're in color. I've observed that color can be up to three times or more expensive than black and white photos. So, yes, if you can go with black and white photos, you will save you money.
I think the big question is, are photos necessary to the subject and genre of your book? If the photos are just "window dressing" (e.g., you talk about computers and use a stock photo of someone using a computer), seriously consider whether they're really necessary.
Also, choose a standard trim size (the height and width measurement) for your book. In self publishing platforms such as Createspace, you are given a choice of standard sizes. If you go with a custom size, that will also increase your cost dramatically.
I'd be curious to know what platform you're using for your print book. If it's KDP or Createspace, it's unusual to see a $25 printing cost. I'm guessing that might have been for color photos, an extremely long book, or it's a custom trim size. Maybe all of the above? It's difficult for me to figure why that might be the case except for these possible reasons.