The original Cities XL forums are mostly dead. Do not use Mediafire links from Reddit threads from 2015. Use these:
One of the most ambitious mods is XL Economy Redux. The original game’s economy collapsed once a city reached 500,000 inhabitants (negative cash flow due to linear cost scaling). Redux recalculates: cities xl platinum mods
Testing by the community (n=37 reported games) shows that Redux enables cities to reach 2 million+ population without bankruptcy, compared to vanilla’s 600k ceiling. The original Cities XL forums are mostly dead
Steam version:
C:\Program Files (x86)\Steam\steamapps\common\Cities XL Platinum Testing by the community (n=37 reported games) shows
Retail/DVD version:
C:\Program Files (x86)\Focus Home Interactive\Cities XL Platinum