From Longman Dictionary of Contemporary Englishmay wellmay wellused to say that there is a good reason for a reaction, question, or feeling ‘What’s all the noise?’ ‘You may well ask.’ → may
Examples from the Corpus
may well ask• What happened to Rodney, you may well ask.• Who is Danny Baker, you may well ask?• You may well ask if such precision is really necessary!• So why, you may well ask, try to grow it then?• The student may well ask what is the solution to this problem.• But why write a novel, you may well ask, when we were aiming to make a movie?• We may well ask: where shall I begin in teaching a brand new congregation?• He didn't know I always carry pistols under my cloak, and he may well ask why. 