As we are very early in development, the balancing isn't final and will still be tweaked and improved to make progression more accurate. As for now, the last available region will have drastically more levels than the previous regions, which will also be exponentially more difficult than previous regions.

Especially the balancing of the last region will not be representative for the final state of the game, but is required to give us some insights into how far people will upgrade the respective regions.