Official institutions will not allow you to directly exchange your currency with star credits. Even the currencies of the territories under the rule of the nine royal families cannot be converted directly into star credits. Of course, you may argue against this, since these nine families possess a large amount of star credits themselves. With their support, the people they rule are basically able to use their local currencies to directly obtain star credits.
In summary, obtaining star credits can be quite difficult, and their exchange rates, even for the currencies of the nine major royal families, can reach rates like 100:1. Moreover, this would be even harder to achieve with the currencies of the lesser-known families. Thus, star credits in the Galactic Federation are nearly as valuable as gold was during Earth's Gold Standard era, or even more valuable; they are indisputably hard currency.
