Theoretically, whether the .org, and .net are registered or unregistered makes little or no effect on the value of the .com
For example, business.com will be worth millions, even if the other extensions were available. However, for high quality domains, you will rarely find they are unregistered in other popular extensions.
However, if the other extensions are registered, it shows there is a demand, so the value of the .com would probably higher, not because the other domains are registered, but because there is a higher demand for that term, or name.