Around here the realtors are all land flippers, so, to buy from them, you have to pay a price high enough to make money for 2 parties. Being able to buy from the longtime owner seems to be the only way to get a deal.
My friend calls it planting the seed, let them know your serious buyer if they ever mean to sale and you’d like first right of refusal on the land. He has purchased several farms this way, usually before they make it to a realtor. Being a good neighbor goes along way to helping you secure that next piece of ground.
Make an offer that will get their attention. What ever the average per acre is going for where you are at should be considered as a minimum if you really want the land purchase to happen. Talk is cheap----money is what it's all about. Make a good enough deal and you should be the next owner in my opinion. GOOD LUCK!