"The Program X ended up costing $0.12 per acre more than the conventional application, and the ProfitZ program was $7.34 per acre under the conventional application. The difference is the methodology of written algothrims in the program. Program X uses a prescription for each zone; ProfitZ uses a multitude of prescriptions based upon intensity of imagery, not just by zone."

That's all well and good, but the $64 question was and is "which one is right?"     Putting on no fertilizer at all will 'save' even more on costs, but that doesn't make it the right answer.  Sometimes less is more, but sometimes less is less.