What is the upper limit of circulating money on earth?
What you are asking, dressed up in economics lingo, is as follows: 

Is there a limit to real gross world product growth?

Short answer

A qualified no.

Longer answer

First of all, developed countries do indeed heavily benefit from the work of developing countries. Globalization has found a way to incorporate cheap labor from overseas for economic growth. However, incorporation of more labor is not the only way the economy grows. Innovation such as new ways to manufacture things more efficiently is another. Just search for "ways in which GDP grows" and most results should apply. But the bottom line is one could imagine a situation were autonomous robots produced expensive cars that were freely available to everyone without having to exploit human labor. Of course, whether the environment could sustain such intense resource usage or whether humans can bring automation/AI to such a point may put practical limits.