How to edit building cost (by Guarder)

First go into GameMechanics, so into TownBuildingSharedStats and then choose faction. So go into the building you want to change. And then you see this (dragon graveyard edited by me):

<?xml version="1.0" encoding="UTF-8"?>
<TownBuildingSharedStats ObjectRecordID="1000051">
  <NameFileRef href="/Text/Game/TownBuildings/Necromancy/Dwelling_7/Name.txt"/>
  <DescriptionFileRef href="/Text/Game/TownBuildings/Necromancy/Dwelling_7/Description.txt"/>
  <Type>TB_DWELLING_7</Type>
  <Upgrade>BLD_UPG_1</Upgrade>
  <Cost>
    <Wood>15</Wood>
    <Ore>10</Ore>
    <Mercury>10</Mercury>
    <Crystal>0</Crystal>
    <Sulfur>0</Sulfur>
    <Gem>0</Gem>
    <Gold>8000</Gold>
  </Cost>
  <ModObjectName>DragonGraveyrd</ModObjectName>
  <dependencies>
    <Item href="/GameMechanics/TownBuildingSharedStats/Necromancy/Fort/Castle.xdb#xpointer(/TownBuildingSharedStats)"/>
  </dependencies>
  <Creature>CREATURE_BONE_DRAGON</Creature>
  <DevLevelNeeded>15</DevLevelNeeded>
  <UIObjectName>Dwelling_7</UIObjectName>
  <UIStackPosition>0</UIStackPosition>
  <Icon href="/UI/TownHall/necropolis/128/d7.xdb#xpointer(/Texture)"/>
</TownBuildingSharedStats>

Copy game mechanics into data folder and take away read-only. You see the red writing over there. Change the numbers to get the building to cost like that. ex: <mercury>10</mercury> to <mercury>1000</mercury>