I'm still looking into this issue, I have no idea honestly what could be causing it. But i can say it happened to me also once, 1 game it happens and another it doesn't it might even be a default game bug going on. I have also given the feedback to Paradox but since they hardly ever communicate back when it comes to bugs no idea if they will ever fix it. But I will keep trying to find what is causing it.

It's me again, with the help from the ck3 mod co-op on discord, I was able to solve the mystery (I think) : If every era has the same date, it seems the game has trouble setting them appart.
Using upon starting the game in 1066 for example. It showed that despite what the ui displayed, the eras were unlocked.

Setting different year for each era ( early med era = 1 ; high med era = 2 ; late med era = 3) solved the issue, the command didn't came back true anymore and upon entering each era, the activity costs did increase accordingly.

However, I don't know if this changes could have any other effects on the mod/game.

I can confirm. This mod currently makes the game think you are in culture_era_late_medieval, if starting 1066 for example. Consequently all costs triple, including tournament price 2200 gold!!!, all tournament contest slots open up etc.

However thx to Tioyo, his little tweak makes things go back to normal. Not sure if there's some other issues that I haven't noticed yet, but so far so good

This is actually a bug with the way cultural eras are setup, you don't actually need to give every era a different start date, you just need to differentiate tribal and the later eras.

The problem is that at setup the cultural era is determined during year 0 and before innovations are loaded, which means every culture starts with 100% of it's 0 civil and military innovations unlocked which immediately moves the culture to the Early Medieval era , which then chains into High and Late , if they have the same date for the same reason. Setting the starting year of Early Medieval to 1 fixes this (and the other eras can also be set to 1 because Early not being unlocked means they don't get checked again until after the innovations are loaded and the game has a proper year.

Early Medieval is already at 1 in this mod only tribal is at 0

Hmmm, that's interesting.

I have a mod that's basically identical to this one in function and I just checked
trigger culture = { has_cultural_era_or_later = culture_era_late_medieval }

and can confirm that as long as Tribal is 0 and others are 1, that that check behaves correctly in both 867 / 1066 (I used the Greeks who are Tribal in 867 and Early Medieval in 1066 and the full set of eras tested properly in both )

Yeah I have no issues either so no idea what can be causing their problems

I had the cost bug but it went away when I set the eras to years 0.1.2. and 3.

Originally posted by Poppy O'Possum:

I had the cost bug but it went away when I set the eras to years 0.1.2. and 3.

It really worked , strange

Originally posted by Eagle-Six:

Originally posted by Poppy O'Possum:

I had the cost bug but it went away when I set the eras to years 0.1.2. and 3.

It really worked , strange

even for the exist save