Upvote:4
The satrapy system meant that many large regions of the empire were given autonomy - as long as they accepted the current Achaemenid king as their overlord complete with tribute and soldiers. And each satrap would be in charge of his own vast region. For the more remote areas of the empire, i.e. Central Asia (not the same as the Middle East) that were mainly inhabited by individual tribes, a satrap could possibly not always have had tight control over his entire domain. Instead, the local tribes themselves would have have been substantial power-brokers. In addition, the Middle Eastern parts of the empire contained once-prominent city states like Babylon and Ur. These areas may have been counted as "provinces" in the Old Testament.
Reference: http://en.wikipedia.org/wiki/Achaemenid_Empire#Government