This is one of those yes-or-no questions to which both yes and no are bad answers, because they are too short.
Your options are
- yes, because I can use my A, B, and C skills and get a chance to work on D and E as I have always wanted to. I know we haven't talked specifics on money yet but I'm confident we'll be able to find a number where we're both happy.
- well, there are several great opportunities available to me, and this job is definitely one that I want, because [rest of the yes answer.]
Just plain yes is a terrible answer. You missed a chance to remind them of the reasons you're such a great fit for this job and would love it so much and should totally be hired on the spot.
Just plain no is a terrible answer. You hurt their feelings for nothing. Try skipping the feelings-hurting and just doing the reasons you're a great fit.
Just plain well kinda but not the only one at the top, maybe tied for the top, is also a terrible answer. Trot out your reasons!
Also, never say "I don't know until I know what the pay will be." It is a ridiculous fiction, demanded by almost all employers, that you choose jobs based only on what you will do all day and possibly where you will live, but not on the salary or benefits (even when they are proud of the salary and benefits.) Every hiring manager's nightmare is an employee who didn't really like the sounds of the job but just wanted the sweet sweet money. So make sure your answer about how they are the top, or tied for the top, or probably-though-I-do-have-a-few-more-questions focuses on what you do all day, not what they will pay you.