The best bet is NOT to hope you can deflect, but instead to prepare for it so you're no longer stumped -- no longer the deer in the headlights! Assume that you will be asked this every single time, just as someone will ask for your name. To come up with a number, you must do research to figure out the going rate for your line of work based on the skills and exp and education you bring to the job. Find out what similar positions pay and base your number on that. You can always state a range and add that it's difficult to give a firm number without really knowing the requirements and challenges of the role, but that you're flexible based on the opportunity. Good luck and don't be scared---preparation is key!