However, it is common to use open-source libraries when building the project. Some of these libraries are third-party, and some of them may have been written by me.
For simple and quick re-usable components, I tend to rewrite them for each project. For more complex debugging & development helper tools, I write and open-source them in my own time, and include in the project based on the open-source license. If the client is paying for my time, they are not included in billable hours, and if they are paying for results delivered, finding a library to do the job is a great way to achieve these results.
Some clients have been surprised by developers asking a lot of money for copyright once they want to update the app, sell licenses or raise funding - for those, including copyright transfer is a selling point for hiring me. If client's don't ask for IP rights, I bring it up myself and explain why they will need it.
I don't think having separate rates for full source code & copyright makes sense. Most of the code is not re-usable between projects, and I don't get any value from keeping it to myself. The only use of charging extra would be if I could then offer cheaper rates to people who don't want IP rights, and raise the rates for those who do: but I'm still doing just as much work for the first group.