Currently AI opponents do not pay maintenance for ships that are stationed, this applies for all difficulties. While this would be OK for higher difficulty levels, normal and below this should not be so.
From GalCiv3AIDefs.xml
<Stats>
<EffectType>Maintenance</EffectType>
<Scope>Global</Scope>
<Target>
<TargetType>Ship</TargetType>
<TargetQualifier>IsStationed</TargetQualifier>
</Target>
<BonusType>Multiplier</BonusType>
<Value>-1.00</Value>
</Stats>
This allows AI opponents to have a very large number of ships without worrying about income. It also hurts them in a way because it gives a false impression on their power, since if they were to send all their stationed ships their economy would collapse.
