Tom Bottorf at GetCollegeFunding has an article that clearly explains why predicting financial aid can be so difficult. Basically, Tom explains that the average financial aid award listed by colleges is just that, an average, and the individual awards can vary dramatically.
I have often discussed the information that families need to know if financial aid is a concern. For those colleges that do not provide 100% of a families need, the understanding of how your statistics, such as grades and test scores compare to the average student, can help estimate whether the college might sweeten your aid offer. If your grades and test scores are on the high side for that college, you may get a better than average aid award. But if you have typical grades and test scores for that school, your aid award may be worse than the “average”.