"Look, I'm not comfortable at haggling, so I'm going to treat this question as a binary search: How about $1,000,000? No? How about $500,000?..."

An educated guess, but also a leap of faith. I've been friends with recruiters, so I guess that makes it a little easier. But you can certainly figure that out from looking at job postings.

But the easy answer is $200k/year is what most people should be aiming to make professionally (even if they don't currently). And so every job switch you make should be a jump in salary. If you're making $120k, there should be nothing wrong with saying you want $160k.

The big issue is just getting yourself psyched up to utter what you want to a recruiter. If you've been paid around $80k for five years with 3% annual raises, it's hard to say to a recruiter, "I want $140k". People tend to internalize that their worth is what that paycheck is, not what the market is willing to pay them. In that sense, it's just a leap of faith you need to make on your part.