Does SQL performance differ between localhost and web server?

My question is pretty simple, does SQL performance differ between a localhost testing environment and a web server environment?

I'd like to get some different perspectives on this, but I'm believing in the idea that this difference is where the term "scalability" was born from. The ability to upscale in SQL transactions without negatively affecting performance. It makes sense when I think of how localhost testing is biased on the performance of one intermittent user on infinite bandwidth compared to hundreds, thousands, and millions of active users on limited bandwidth.

Bonus: If anyone has opinions on this question as well then you would be doing me a social favor by sharing your expertise. What other types of performance are affected in a "passive localhost activity VS. active web server activity" comparison?

Extra Credit: What types of performance are NOT affected in the same comparison?