Is "at" necessary here because it seems to be okay by saying "eat away profits"?
Native speaker’s answer
Rebecca
In this case, "at" is a necessary part of the sentence as the full expression is "to eat away at (something)." If we were using this expression in reference to food (to eat something heartily), then the "at" would most likely not be required. Ex: Everyone, eat away to your heart's content! We have lots of food! Ex: Continuous bad weather has eaten away at the restaurant's profits.