Exactly, the value is in the fact that it's bundled: instructions and everything you need to make the circuit, exactly the same components used in the manual.

As for getting assorted components to complement these bundles or other projects: SparkFun makes it easy for the US.

But being in the EU (and caring about ROHS and CE) I use these to fill the gap:

http://www.exp-tech.de/

https://www.tinkersoup.de/en/

http://www.watterott.com/