I have a DB 60 high speed 36 row 20 inch planter. It has about every option on it including tracks, hydraulic down force, hydraulic row cleaners and air down force on closing wheels. I put on the Schaffert Rebounders with Y-Not Splitters to apply 10 gal. of 10/34/00 in-furrow. I use the Y-Nots as it applies the fertilizer beside the seed, not on it.
I say this set-up is the real deal! When I check stands there is never a double, never a skip. If a plant is missing, dig down and the seed is there. Happens very seldom, though.
I apply fertilizer for two reasons: 1) a carrier for insecticide; 2) the corn moisture in the fall will be 2 to 3 points less and the yield slightly more.
As far as cost goes, the only cost is setting up the planter. Whatever units I put on with the planter, I subtract off the spread fertilizer. I believe high yields are obtained by a lot of little things working together. My APH is 239 per acre on rolling ground near the Mississippi.