With rental prices in southern Iowa in the $200/acre range and inputs on top of that I would say and acre of corn could cost you $550-700 if your paying for input cost only.
His insurance revenue guarantee per acre on corn with a 135 bushel average yield at 80% coverage would be $610 per acre. (135*.8=108 bu/acre*$5.65 spring price = $610.2
Soybeans with a 40 bushel average and 80% revenue protection would be as follows: 40*.8= 32bu * 12.87 (spring price for soybeans)= $411.84
The variables of aph yield and coverage level can be adjusted to fit your area/farmer. I would say this would be the best way to buy standing crops since they will forfeit their insurance on those acres by leaving them in past the harvest date.