I edited the file "GalCiv3GlobalDefs.xml" from %Steam library\steamapps\common\Galactic Civilizations III\DLC\EXP2_Crusade\Game% and changed the
<CulturalAlignmentBiasSamePyramidGrowthMultiplier> and <CulturalAlignmentBiasOtherPyramidGrowthMultiplier> values.

*** If you already have a mod changes the "GalCiv3GlobalDefs.xml" file***, you can mod it yourself by locating the lines above and changing the value at your own taste.

Here is the full block from by game file, including the comments:

    <!-- To test this growth rate, go to http://www.google.com and draw a graph by typing:
        
y = CulturalAlignmentBiasSamePyramidGrowthExponentialMult * x^CulturalAlignmentBiasOtherPyramidGrowthExponent
+ x*BasePrice*CulturalAlignmentBiasOtherPyramidGrowthMultiplier
        
...where you replace CulturalAlignmentBiasOtherPyramidGrowthExponent, BasePrice, and
CulturalAlignmentBiasOtherPyramidGrowthMultiplier with your testing values.
        
The X axis represents the number of unlocked traits.
The Y axis is the resulting price. -->
    <CulturalAlignmentBiasSamePyramidGrowthExponent>1.0</CulturalAlignmentBiasSamePyramidGrowthExponent>
    <CulturalAlignmentBiasSamePyramidGrowthExponentialMult>0.0</CulturalAlignmentBiasSamePyramidGrowthExponentialMult>
    <CulturalAlignmentBiasSamePyramidGrowthMultiplier>0.5</CulturalAlignmentBiasSamePyramidGrowthMultiplier>

    <!-- To test this growth rate, go to http://www.google.com and draw a graph by typing:
        
y = CulturalAlignmentBiasOtherPyramidGrowthExponentialMult * x^CulturalAlignmentBiasOtherPyramidGrowthExponent
+ x*BasePrice*CulturalAlignmentBiasOtherPyramidGrowthMultiplier
        
...where you replace CulturalAlignmentBiasOtherPyramidGrowthExponent, BasePrice, and
CulturalAlignmentBiasOtherPyramidGrowthMultiplier with your testing values.
        
The X axis represents the number of unlocked traits.
The Y axis is the resulting price. -->
    <CulturalAlignmentBiasOtherPyramidGrowthExponent>1.0</CulturalAlignmentBiasOtherPyramidGrowthExponent>
        <CulturalAlignmentBiasOtherPyramidGrowthExponentialMult>0.0</CulturalAlignmentBiasOtherPyramidGrowthExponentialMult>
        <CulturalAlignmentBiasOtherPyramidGrowthMultiplier>0.1</CulturalAlignmentBiasOtherPyramidGrowthMultiplier>