Increase of Great people points level

Each Great person costs some amount of GP points (those are usually produced by special districts and possibly by some wonders).

After each GP is "made" (either by GP accumulation or by purchase), the cost of the next one usually goes up substantially. This can be used strategically - if the race for a GP becomes close, player can purchase the GP and never allow other players to have any GP of that type.

The cost increase does not happen always though, sometimes even on really low costs (such as 120 points). What are the factors that contribute to that (or stop increase of the cost altogether)?

Solution 1:

The game mechanics for Great People is straight forward. Great people are arranged in eras. Each era holds a set amount of Great People from that era in a random order. Once the pool of Great People from that era has been depleted, the Great People from the following era become available and the cost doubles.

This is why, for example, all Great Prophets cost the same.