Best price for the farmer is always to sell it themselves, but you can only sell a limited amount that way. In Netherland, some smaller farms have a little stall outside where they sell their produce. It's very cheap and fresh for the customer, and the farmer gets a much better price. But the total amount they're selling that way is never going to be big. I suspect it's just a nice bonus to them.

My brother in law has cows, and he recently switched to producing organic milk. That gets him a much better price, and he also recently started making his own cheese and grow his own grain. I love the diversification and we buy directly from him, but his reach is more limited than when he just has Campina pick up all his milk (which still happens).