1400!!! lets gooo also ive been doing more math. After getting all 18 tiles you would have a tile score of 38. if the remaining tiles were all oasis habitats (6 points) you would have a tile score of 146 meaning the absolute max board score is 2,628. BUT that would take 108 perfect moves So it is impossible. More realisticly if we can get 2/3rds of our turns to be "perfect" and create 10 oasis habitats with the 18 other tiles we get a score of 1,764+ whatever the last 10 tiles end up as from the last 1/3 of the moves.
TLDR: Between 1800-2000 is what I would call a "Perfect game" and we are rapidly approching that benchmark 