Emphasizing the sum was greater or less than expected value
Based on your desire for an alternative to greater than/less than, I would go with The sum exceeds X and The sum falls short of Y. @Jim noted the latter in his comment on your question.
Exceeds and falls short of are stronger that is greater than and is less than (they are stronger verbs), and they are natural antonyms, which might satisfy your desire for same.
Also, exceeds is one word, while is greater than is three words.