Good question

If the farmer is very poor, it will be easy for him to get the incentive, he need to continuously sell his products to get money, and buy other things he want

Actually, all classical economics are based on the assumption that the farmer's incentive is kept forever due to that human's desire is endless

But, if the farmer is very rich, it will be much more difficult for him to get enough incentive to work

So, chasing for profit is the last incentive for a rich society?