If you plant 1k you have a 1% chance of getting a money tree with 3k on it.
If you plant 10k you have a 10% chance of getting a money tree with 30k on it.
If you plant 30k you have a 30% chance of getting a money tree with 90k on it.
If you plant 50k you have a 50% chance of getting a money tree with 90k on it.
If you plant 100k you have a 100% chance of getting a money tree with 90k on it.
Does that help at all? Basically for every 1k you plant theres an extra 1% chance that it will grow and you always get 3 times the amount you plant. Although you can't get more than 90k per tree.