In the second tab there is a price stated for the fruits. This is the value you get for every fruit you hand in. The NPC value of the item you get determines how many you get. For example: ... Coda has a buy back of 1000. It gives Animal Bones. The NPC buys animal bones for 100. This means that for every seed you hand in you would get 10 Animal Bones. The real values differ of course but this is the way to calculate how many mats you get. (I think :P)
Hmm, so what you mean is : Take some mat to an NPC and see what it'll pay for it. Then check the manor's buy back price of the fruit and multiply/divide the 2 sums?