For C and C++, you can get effectively equivalent working drafts for free. For C++, you can actually compile the PDF that gets sent to ISO to put the official markings on yourself. Here is C++17: https://github.com/cplusplus/draft/tree/c++17 .

If you have a contractual obligation that requires to exactly use a specific version of C/C++, then you'll need to pay money for the actual specification. In pretty much any other situation, the drafts are sufficient and perhaps even better (because they will have incorporated some errata).

Isn't it that all ISO standards cost money?

I'm sure you were perfectly aware of it, but C and C++ working drafts are almost identical (I think? Never bought an ISO version), and available for free from open-std.org. For example, http://www.open-std.org/jtc1/sc22/wg21/docs/standards