Freeciv

My personal suggestion for how to have our cake and eat it too would be either a simple ruleset switch for which improvement genera should have their buy cost doubled, or an all-out set of multipliers (one for each genus) to directly regulate buy costs.

The Multiplayer ruleset was done a long time ago as a 'fix' or 'adjustment' for games involving large numbers of human players. It's typically being used in large map games of 50+ players. One of the fixes or workarounds it did for game play was to allow duplications of Wonders by making every Wonder a Small Wonder. Otherwise, with 50+ players, whoever gets a Wonder which is a major advantage becomes a very rare stroke of luck and advantage over all the other players.

While the 'fix' to make Small Wonders 2g/p may make a small improvement for single player and games with <12 human players, it completely breaks the game balance of the Multiplayer ruleset and the large following of people who enjoy games of 50+ players.

Game Balance is now completely off in so many ways.
1. Wonders with very large power become rather cheap to buy. Players report they don't even use Caravans and just buy them immediately, often on the turn they are available.

2. The bonus effect of the wonder compared to its low buy-off cost becomes imbalanced to where there is little strategic decision on whether to buy a Wonder. For best expert play, it now becomes obligatory to buy every Wonder like cheap candy, just to keep even with everyone else who is also buying every Wonder.

3. The noted advantage of trade-based governments (Repub., Demo.) over production-based governments (Fundamentalism, Monarchy, Communism) is wildly exaggerated. It is now that much easier for governments getting +1 trade per tile to buy off 1 prod for 2 gold, whereas production-based economies have less gold, and the use of caravans to make wonders is now at an economic ratio disadvantage to purchasing with gold. Whereas before, it was possible for a good leader to be competitive with strategies using non-trade based governments for part or most of the game, this one change forces every expert player into the same trade-based government strategies and wrecks diversity of strategic creatvity and game play.

4. 4g/prod created an efficiency ratio where it was more efficient to use Caravans to build Wonders, rather than using gold. Since it is now more efficient to use gold to buy Wonders, Caravans become not only useless units but every city continues to make its own improvements without ever bothering to plan or contribute to a Wonder, since its excess gold is enough for Wonders while it continues making its own improvements.

We previously considered adjusting buy cost in gna bug #22089 . We came to basically the same design. We also considered letting Building_Buy_Cost_Pct=-100 act as "prevent buy", and adjusting unit buy cost too (with a separate effect, which the design here leaves room for).