On the last (and only) paperback I did through Amazon, I put something like "This is the last page of the book." on the very last page of the book, an even-numbered page. Amazon added several blank (but numbered) pages after that page.

So, yeah, I'm not going to worry about whether making my chapters start on the right hand side is going to "waste" paper or not.
Keep in mind that Amazon may well print in four-page "signatures" (four pages printed on each piece of paper). That means that if a book ends up being a number of pages not divisible by four, there could be excess at the end, up to three pages. If it uses larger initial paper stock and therefor a larger signature, the number could be greater.
I just looked at the two (forgot I had two) paperbacks I have on Amazon.
First book has 744 pages in my file. That's divisible by both 4 and 8 but not 16. So, if they use signatures of 4 or 8, then it should be good without adding extra pages. If they use signatures of 16, then the final page count should be 752. Amazon added 6 pages for a total of 750 which is not divisible by 4, 8 or 16.
Second book has 212 pages in my file. That's divisible by 4 but not 8 or 16. Again, if they use signatures of 4, it should be good. If they use signatures of 8, the final page count should be 216. If they use signatures of 16, the final page count should be 224. Amazon added 4 pages to the book bringing it up to 216. That matches a signature of 8.
So, I don't know what that tells us. If they print using signatures, they should have added 0 or 8 pages to the first book and 0, 4 or 8 to the second book. But they added 6 to the first and 4 to the second.
