As you evaluate the cost of inputs, consider this: Only focusing on expenses without subsequent income changes is misleading. The most profitable plan uses the most profitable inputs. Is a starter fertilizer one of those inputs? The authors look at university and grower research under various conditions to see when a starter fertilizer offers economic benefits.
A review of 10 years of soybean research shows that reducing your seeding rate from 150,000 to 120,000 seeds/acre can result in a $10.69/acre savings without affecting yield (assuming a $60/unit seed cost at 140,000 seeds/unit).