This is a lot harder than you make it sound. I have worked in sectors where people would worry that asking that question would terminate the interview - hospitality for one.
Then, at least you can go home knowing that you are already making what the market can bear, and you aren't leaving money on the table.
Asking what question?
I did not understand this, and still don't.
If there's an advertised wage - $x/hr - and you know this going in, yet ask for more, I can see an interview being terminated.
If there's not an advertised wage, and I ask for something ($x/hr) I can't see how that would lead to an interview being terminated.