PhD applications: ethics of not informing other universities after accepting an offer I have accepted a PhD offer from university A. I have informed a not so prestigious university D that they should dismiss my application (they invited me for an interview, offered me to pay the flight, etc.). I am still waiting to hear from very prestigious universities B and C (which, as A, are top 10 in most rankings). Is it ethically acceptable for me to wait for the decisions of B and C and inform them about my choice of A afterwards? I am curious whether they would have taken me. Informing B and C late means wasting their time, but I paid application fees for B and C.

To clarify: I do not intend to attend either of B or C.
I think you should withdraw your applications from B and C.

By keeping your application active, not only are you wasting the committee's time, you are potentially hurting other students.  Most graduate programs can only accept a certain number of students per year, but there may be many more applicants who would still be well qualified and able to succeed.  If the committee accepts your application, that means they are denying admission to someone else who might be equally deserving.  If you withdraw now, you open that space for someone else.