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In a word NO. They are copy righted and technically it is illegal to even copy the knowledge reviews (that is why they are attached and aren't made to tear out).
Summary: 1) Is the manual a current edition? 2) How does the dive centre process it's certifications with PADI? 3) What form of RDP do they use with the course? 4) Can they separate the cost of a manual, if the certification and RDP are also provided? 5) How much actual deduction can they give you, even if they can separate the manual cost?
If the knowledge reviews were still in the book, there wouldn't be a problem.
Copyrighting only prevents duplication of the materials. There's nothing to stop a student writing their answers onto a blank piece of paper or even completing them electronically/word processed, thus preserving the Knowledge Reviews in the book. Likewise, there is no PADI standard that dictates that students must complete the knowledge reviews by writing in their manual.
If the OP's manual didn't have the Knowledge Reviews (i.e. they had been torn out on a previous course), then they wouldn't have access to the required materials and would have to purchase a new manual.
Since the PADI standards changed a few years ago...and dive centers have no requirement to tear out and keep knowledge reviews... there is a good chance that they'll still be in the manual.
So far I have not been faced with the OP's situation....all of mine have had the husband and wife in class together and then they are required to have their own set of manuals. (shop requires it - mo money)