What exactly is the difference in quality fertilizers vs. cheaper fertilizers?
I say this in reference to two fertilizers that are labeled the same. If they are labeled the same, then by law they contain the same product inside the bag. So why would one cost more than the other?
It typically comes down to how it was generated, mixed and blended. To get a good, even coverage of all the nutrients, you want all of the granules and particles to be of consistent size and weight. High quality fertilizers are going to be broken down and mixed in a way that provides even coverage across your lawn.
In cheaper fertilizers, you will tend to find more variation in the size and weight of the granules and particles. Heavier and larger granules will be distributed at different distances than lighter, smaller granules, thus potentially resulting in uneven distribution of nutrients across your lawn.