The antonyms for the word "over prizes" could be countless. It depends on the context of the phrase. For instance, if we are referring to a competition or a contest, antonyms to "over prizes" could include words like, "no award," "no prizes," "no winner," "no reward." If we take the phrase in the sense of being "too generous" or "giving away too much," then antonyms would include words like "stingy," "mean," "tightfisted," "parsimonious." Nevertheless, depending on the context, any word that is the opposite of "over prizes" could be considered an antonym. Overall, it is essential to understand the context of a word before determining its antonym.