This chart seems to support my point. 6 full trees (36 picks) are dramatically more expensive to reach than 30 picks are in vanilla. In fact, they're more expensive to reach than 36 picks are in vanilla. So you have made a cultural victory harder to achieve.
I would be very surprised if culture production was 50% higher in TBC.
Policy rate is income/cost, and the chart I linked only showed costs. Consider a size-20 city with each of the cultural buildings up to and including Museums.
Originally we got about 18

:
- 2 + 3 + 4 + 5 = 14 from buildings
- 2 + 2 = 4 from artists
In the mod it's currently 40

:
- 2 + 3 + 10 = 15 from buildings
- 3 + 3 + 6 = 12 from artists
- (15 + 12) * 1.5 = 40 total
This change mainly applies to the post-Opera House era however... around the time the increasing costs kick in.
Look at the chart again - the baseline is the 100% line and the vast amount of policies are below 75% of vanilla costs!
Seek's point is actually important even though the chart it does show cumulative costs:
- We have fewer cities in the early game.
- The policy cost reducers are later in the late game (representation, free speech, Christo).
- Our last two policies are free.
Since policy costs are on average shifted from the beginning to the end of the game, it reduces the total culture required for victory.
I've completed two culture victories since the main policy changes were completed;
one is detailed in the thread I linked:
I achieved victory on turn 351 in 1650 AD with a score of 2743 and 9 cities. I had income of 1300

/turn and 1100

/turn (1600

/turn during the continuous golden age at the end of the game). My score for this game was lower than my typical Domination victories, but 54% higher than my 5-city 1775-score cultural victory as Kamehameha.
I demonstrated in the thread that empire size is not a significant factor for cultural victories. What does matter is warfare: I feel somewhat confident a peaceful game is required to achieve the fastest cultural victory. Any significant military expenditure costs too much to be beneficial for this victory type. We lose science (DoFs), production (building units), and gold (maintenance).
@Questdog
Do you play with no citystates on the map, or just not interact with them? In general I think culture players get cultural citystates because it converts gold to culture, something useful when going for this victory type. 8 out of 10 trees are useful for a cultural victory, and 6 are needed, so we can pick the 2 out of those 8 we want to leave out.
In version 7.2.3, I had a scout that entered a goody hut and was promoted to an explorer, but lost the "Ignores Terrain Cost" Promo. Shouldn't Explorers have this trait as well, or was this by design?
I did this to avoid overpowering Explorers. At 3

they still move at a rate of 2 through most rough terrain, same as Scouts. They move slower in rough+hill or over rivers, but faster in open terrain, so the movement is about the same.
I also want to be careful about explorer vs pikeman balance. They've got the same strength and cost, so it's important for explorers to be slightly weaker in combat than pikes. I think this is accomplished since explorers are much weaker on the attack (no shock/drill to improve attack strength), and it's very difficult to get Survivalism III in the first half of the game, so they're not terribly good at defense yet either. The advantage of explorers is their higher speed, sight range, and they complete the scout -> explorer -> lancer chain so we can upgrade our units. These characteristics make them great Medics.