Buyback of crops - a noob asks....

So I got into the manor system somewhat belatedly, and so far I've managed to beat the non humans a few times on some decent crops/seeds (chlly cobols/desert cobols/blue codas).

One thing about the whole system I really can't get my head round tho - how many mats I'm likely to get as the payoff for turning them in. For example, the other day I turned in 45 blue cobas and got back 8 crafted leather from Aden. Not bad I thought. Later the same day turned in 200 crops and only got 18 :/ So my question is, is there a set crop:mat ratio? Important to note here the buybacks were at the same rate (1000 I think; Aden was the only place buying). Another time I put in 150 desert cobols and got 10 dmp; next day (again at same buyback price from Giran, 1000a) I put in max available for the day, 498, and got 31 dmp (I was expecting 33 or maybe 34, based on the earlier 15:1 ratio).

I'm trying to avoid wasting 'remainder' crops, especially now as I managed tog et hold of some golden coba last night ;)

How much VoP can I expect to receive (provided I beat the automatons turning it in of course) for each crop based on the current buyback of 1250 in Aden or 2000 in Innadril?

I'm not sure if price I bought the seeds at makes a difference, but they were 800 per I think.

Thanks in advance

Very easy just take one of the mats u wana get to a npc he always pays 50% of the gameworth for it.
Now double that price and you know how much money u have to accumulate from crop to get one material out.

Also if some manor buys back crop for less money u need more crop and vice versa.

e.g

red cozle gives stem
npc shop offers 50a for stem
stem must be worth 100a

you go to giran and they pay 2000a for red cozle
1 red cozle will give you 20 stem

you go to oren and they pay 1450 for red cozzle
1 red cozle will give you 14 stem (you lose 50a worth of mats)