Not according to the xml. It reduces Manufacturing Cost, which is production cost and rush cost.
Example:-
Tech Reducing Cost:
<Stats>
<EffectType>ManufacturingCost</EffectType>
<Scope>Global</Scope>
<Target>
<TargetType>Improvement</TargetType>
<ImprovementType>Manufacturing</ImprovementType>
</Target>
<BonusType>Multiplier</BonusType>
<Value>-0.15</Value>
</Stats>
Improvement Build Cost (Basic Factory):
<Stats>
<EffectType>ManufacturingCost</EffectType>
<Scope>Queue</Scope>
<Target>
<TargetType>Improvement</TargetType>
</Target>
<BonusType>Flat</BonusType>
<Value>30</Value>
</Stats>
It is more noticable with rush buying since Rush buying by default costs 10x the production cost:-
<RushCostMultiplier>10</RushCostMultiplier>