without having to do a lot of xml programming?
XML isn't programming; it's practically plaintext. The portions you'd be altering would be, at least-and there's no "recompiling" to be done, either, although you do have to start a new game to see the changes.
Step 1: Right click on PlanetImprovements.xml in the \Data\English folder in the appropriate GC2 folder and select Open With, then select Notepad.
Step 2: Use the find function to locate the building you want to change the cost of, let's say Industrial Sector.
You get the following (this is from TA but the procedure is the same regardless):
<Improvement>
<S_InternalName>Industrial Sector</S_InternalName>
<S_Name>Industrial Sector</S_Name>
<AI>20</AI>
<S_UpgradeTarget>Manufacturing Center</S_UpgradeTarget>
<S_Type>Normal</S_Type>
<Maintenance>10</Maintenance>
<Cost>400</Cost>
<S_BriefDescription>Increases manufacturing.</S_BriefDescription>
<S_Description>A high density manufacturing area.</S_Description>
<S_IconName>Engine Turbo Design Center_64.png</S_IconName>
<S_QueryGraphicName>Engine_Turbo_Design_Center.png</S_QueryGraphicName>
<CanHaveAgents>1</CanHaveAgents>
<S_TechRequirement>Industrial Sector</S_TechRequirement>
<Industry>12</Industry>
</Improvement>
Step 3: Change <Cost>400</Cost to, for instance, <Cost>200</Cost>
Step 4: Save as and place it in your mods folder, or overwrite if you don't mind playing a modded base game (but save it somewhere anyway just so it doesn't get overwritten by updates), and keep in mind that you can't use most mods (this type included) in the Metaverse, if you're into that kind of thing.
Modding tech costs is just as simple, except they're in TechTree.xml, and with TA each civ gets their own branch/variant located in the TechTrees folder, so it's not all in the same file anymore.
