Okay, let us get the right numbers on the table, at least, if this is to become some sort of sensible decision.
In the demo, culture conversion costs 25 DMP per taxvalue. There is only one cultural conversion cost reduction in the game, the -80% cost reduction for being overseas. These numbers are all in the demo, available for anybody who cares to test.
Examining the benefits of cultural conversion, one quickly realizes that while apparently significant, in most cases conversion has little impact on your realm as a whole unless converted areas make up the majority of your realm.
What you eliminate by cultural conversion of a non-accepted culture is:
- The -2 RR modifier. This may or may not be important to you depending on your realm's overall stability and how scared you are of rebels.
- The -33% local tax modifier. It is important to remember that this stacks additively with all other local tax modifiers, not multiplicatively.
- -33% local manpower modifier. It is important to remember that this stacks additively with all other local tax modifiers, not multiplicatively.
- -2% local missionary strength. Since you cannot culture convert a province until you have converted it to your religion, eliminating this effect is utterly irrelevant to you, unless you intend to first culture convert it, then change your country's religion, and then change the province's religion. Which is a really special case that is unlikely to occur except for Catholic countries that do not intend to stay so after the Reformation.
This leads me to the following conclusions:
- It is cheap to convert overseas and almost always worth it if you expect to hang on to the territory in the long run. Especially for the colonial real estate, which mostly takes place in really low-level provinces, this is a steal. . The effects of the cultural conversion are minor, but at 5 DMP per taxvalue it is worth it in the long run in SP and, for MP, in most cases where no reversal of fortune is expected in the short run.
- It is damn expensive to convert non-overseas and rarely worth it unless you have nothing else to spend your DMP on and/or desperately need the extra manpower. How frequently this occurs depends to a large degree on techgroup and luck with monarchs. My personal opinion is that cultural conversion of non-overseas is pretty much the last thing a player should want to spend DMP on unless he is deliberately retarding his diplomatic tech growth in order to westernize.
Cultural conversion is an optional extra, and its value greatly depends on whether you are converting overseas or not. Pretending that EU4 culture as a whole is a joke or meaningless on the grounds of experiments with overseas conversion only is missing this critical point.
Now, I would urge people arguing that this is too expensive/too cheap to keep the mathematics of culture conversion in mind even if you disagree with my conclusions as to when it is appropriate or sensible for a player to use it in-game.
For a fun thought experiment, converting the entire Iberian peninsula, which has roughly 200 base tax when temples are built, would cost 5000 DMP. Now, I am sure that some of you will argue that "that is much too cheap and easy based on this or that historical argument, because it should be impossible/insanely difficult/whatever", and I am not saying that you are wrong, but the flip side to this is,
which human player would actually do this?.
The price of any gameplay action needs to be measured against the income of the currency in question and the gameplay effects, and to which degree the results help or hinders the game design, not against abstract "what should be possible", as the former is what determines how it will be used by players while playing, not the latter.
(And no, I am not suggesting that converting the entire Iberian peninsula is the be-all-and-end-all example for discussion - how about converting all of France, all of central Germany, all of... you know, all of various other regions that frequently change hands in EU games. I chose the Iberian peninsula for the example because it was the easiest region for me to quickly tally the taxvalues of and everybody has a good idea of how large - and how small - a part of Europe it really is, which makes it easy to put the 5000 DMP cost in perspective.)