Boy talk about an open question the OP, one that truly has no answer or every answer.
Why do I say that you ask? Because the price per acre varies hugely dependent on many facts. Some of those facts are as follows.
Access to
water.
Size of parcel, larger tracts cost less per acre.
Location, location and LOCATION
Soil
Right of way or actual access off a road.
Climate
Seasons
Flat, mountain, valley, prairie, costal
Solar exposure for crops and or power
wind for power
There is no answer to such an open question. It needs to be want and area or climate specific. IE: I want to live where it's always warm or cold or that truly has 4 seasons. I want to live in the piedmont region or the grass lands or the mountains. I want to live where I can grow --- or where there are no ----.
There is NO one size fits all answer to this question.