I'm working on a plugin for some software that I'm planning on selling someday. The software I'm making it for has both a C++ SDK and a Python SDK.
The C++ SDK documentation appears incomplete in certain areas and isn't documented that well.
The Python SDK docs appear more complete and in general are much easier to work with.
So I'm trying to decide if I want to go through the potential trouble of building a C++ plugin instead of a Python plugin to sell. About the only thing that makes me want to do a C++ plugin is that in my mind, a "C++ plugin" might be an easier sell than a "Python plugin". A lot of programmers out there don't even considered writing Python to be real "programming".
Do you think that potential customers might say "Why would I pay money for a measly little Python script?"?  As opposed to "Oh it was written in C++ so the guy must be a decent programmer"?
Writing the Python plugin would be faster. Both plugins would look and behave exactly the same. The C++ plugin might be faster in certain spots, but for the type of plugin this is, that's not a huge deal.
So my question is, would a Python plugin be considered not as professional/sellable as a C++ plugin, even if it looks and acts EXACTLY the same as a C++ plugin?
A lot of programmers out there don't even considered writing Python to be real "programming".

A lot of "programmers" out there are incompetent, too.

Do you think that potential customers might say "Why would I pay money for a measly little Python script?"?

I'm sure it depends on the type of software, but I can tell you that my program's customers have little interest in what we use to develop our product, and I doubt most of them know that the software is written in C++.  They just care that it works.

So my question is, would a Python plugin be considered not as professional/sellable as a C++ plugin, even if it looks and acts EXACTLY the same as a C++ plugin?

No.
Is Python-based software considered less-professional than C++/compiled software?